# Live Sand Dollars in Costa Rica

Updated on May 14, 2015

## Sand Dollars and Math

One day at the beach in Costa Rica my daughter and I were digging in the sand making sandcastles when we ran across a live sand dollar. Finding a dead exoskeleton would have been exciting but finding a live sand dollar was unbelievable!

We held it in our hands and felt the tiny hairs on the underside of its body tickle our skin as the animal tried to get away from us and wiggle its way back down into the sand. We turned it over and watched its mouth moving in the center of its flat body.We set it down in the sand and watched it filter sand and water through its body and out the five holes that radiate out from the center.

Then we started to feel just under the surface of the sand as the tide washes the waves back and forth and began to find more sand dollars. At first we found one or two. Then we found them by the tens. We soon realized that there were hundreds, thousands and possibly millions of sand dollars right there on that beach.

We spent the rest of the day observing, drawing, measuring and counting sand dollars. This lens is about the math that can be learned at the beach while observing sand dollars.

## Sand Dollars and Math

Many people think that math can only be found in textbooks, that learning only takes place in a classroom and that math is a boring but necessary evil.

The day we found the sand dollars was filled with fun and exciting activities that helped us describe our observations of the sand dollars while working on basic math skills. We spent the day observing, drawing, measuring and counting sand dollars.

Since then I have added many more activities to this unit study and found that children love to learn math when it involves the chance to learn in an exciting environment such as the beach and about a live animal living in that environment that they may never have seen before, such as the sand dollar.

Math that can be learned at the beach while observing sand dollarsl

## What do you need for your day at the Beach?

• Plenty of sunscreen
• Water to drink.
• An underwater clipboard
• A waterproof digital camera
• A guidebook to the seashore (keep in a Ziploc bag)

You also might like a stopwatch to see how fast the sand dollars can bury themselves back under the sand, a compass to see if they always go into the sand in the same direction and a tape measure to measure the diameter of the sand dollars.

I keep these things in a bag in the back of my car so that we are always prepared for unexpected math adventures at the beach.

## Adding, Multiplying and even Dividing Sand Dollars

As you walk along the beach you will find many beautiful shells, pieces of seaweed and sand dollar tests, "sand dollar shells". It can be fun to collect them and then use them in counting games.

For very young children that might mean just count to 3 or 5. For older children you might arrange them into groups of 10 and then count by tens to see how many you have collected.

You probably won't find hundreds of sand dollars but if you find say, five sand dollar tests, each with five holes you can multiply to see how many holes there are all together.

What if you wanted to pretend to feed a pile of 20 small shells to the sand dollars. How could you divide those shells evenly among the sand dollars?

## Sand Dollar Ridges

Look for the hard white sand dollars along the tideline amongst the seaweed and shells. These are the exoskeletons or the dead remains of sand dollars. Look for growth rings along the edges of these plates.

Separate your sand dollar tests (the dead "shell" of the sand dollar) by age. What is the average at which your sand dollars died?

You can use your underwater tablet to make a graph representing the average lifespan of the sand dollars you found on the beach.

## Looking for Symmetry in Sand dollars

Study the exoskeleton of a sand dollar and you will quickly find the line of symmetry that divides it into two equal parts.

## Sand Dollar Worksheets

For the younger children it's fun to print out these sand dollars and try to find the two that match.

For the older children, challenge them to make more Sand Dollar Twins.

## Sand Dollar Number Line - Counting by 5's with Sand Dollars

When you get back home you can start a number line using sand dollar mini accents for the multiples of 5. We used blank squares for the numbers 1-4, a sand dollar paper for 5 and then again blank squares for 6-9.

We also used the sand dollar mini accents for writing the numbers 1-5 next to each of the holes in the sand dollar and then writing a large 5 in the middle. One of my children really enjoyed this activity and continued on up to 100.

Later on we used these to remember the numbers that come right before the multiples of 5 when subtracting. We played a game like a spelling bee and used the cards when asking questions like what number is 3 less than 10.

## Watching the movements of a Sand Dollar - Measuring the Speed of a Sand Dollar

Notice how the hairs on the edge of the sand dollar move in waves to help the sand dollar to travel across the sand. The sand dollar leaves circles showing that there are more rows of hairs on the underside of its body helping it move.

Using a tape measure and a stop watch you can determine the speed of a sand dollar. How many inches per minute can a sand dollar travel? How long would it take the sand dollar to travel a yard or a meter? a mile?

Does the sand dollar always head toward its shadow? What happens if you block the sun? Can blocking the sun confuse the sand dollar's sense of direction? If you measure the length of the sand dollar's shadow and its height can you determine the angle of the sun?

A beach in Costa Rica is the perfect classroom for homeschooling.

## Finding Sand Dollars on the Beach

Sand dollars can be found on the beach just under the sand at low tide in the tidal zone. Run your hands through the water saturated sand to feel for them. The are not harmful and do not bite. When you hold them in your hands they tickle as their hairs quickly move trying to get back down under the sand.

Sand dollars need to stay moist so don't keep them out of the water very long.

## Comparing Live Sand Dollars with their Tests

Look for the tests of sand dollars that wash up with the seaweed at the tide line. These are the white remains of dead sand dollars that some call the shells. Compare the tests with the live sand dollars. Try to find ones of similar size and compare them. How much space does the live sand dollar take up in comparison to its test?

## Picking up a Live Sand Dollar

Sand Dollars are fine to pick up. They don't bite, sting or give you a rash. The bottom side of the sand dollar is covered with suction cups that tickle as the sand dollar glides across your hand. Turn it over to see the suction cups. Remember to return the sand dollar to where you found it after just a short time as the sand dollar needs to be in the water to breath.

## Doves in the Sand Dollar

Now that you are back from the beach it's time to whip up a batch of Sand Dollar Cookies. Use fractions to measure the ingredients. The more the merrier so use your knowledge to multiple fractions as you double or triple the recipe.

Once the cookies come out of the oven it's time to divide them equally.

If there is no time to make the cookies you can't do better than to order some from Plum Island Cookie Company. Figure out the cost including tax, handling and shipping. How much would that be if you order two boxes?

How many cookies will there be for each person in your family if you divide them equally? How about if you invite your grandparents?

* 3/4 C butter

* 1 cup sugar

* 2 eggs

* 1/2 Teas. vanilla

* 2 1/2 C flour

* 1 Teas. baking powder

* 1 Teas. salt

Procedure:

1. Mix the butter, sugar, eggs, and vanilla thoroughly.

2. Add flour, baking powder and salt.

3. Mix and chill the dough for one hour.

4. Roll out the dough on a floured surface to 1/8"-1/4" thick.

5. Cut out cookies using a 3" cutter or water glass.

7. Draw a star in the center of each cookie with a dull knife.

8. Bake at 400 degrees for 7 mins.

Recipe Credit: Cape Treasures

## Dividing the Sand Dollar Cookies - Sand Dollar Division

Read the story of the children trying to divide the cookies evenly as more and more friends show up at the door in the story The Doorbell Rang. Then make some sand dollar cookies and practice some division and of course, subtraction.

## Playdough Sand Dollars - Make your own Sand Dollars

Mix up some Playdough and add some sand. Make your own playdough sand dollars. Use the test of real sand dollars to press the details of the sand dollars into the ones you are making.

Once you have a pile of Sand Dollars you can use them as math manipulatives, adding and subtracting them from a beach in the sensory table.

How else could you use your playdough Sand Dollars?

1 cup flour

1 cup of water

1/2 cup of salt

2 tablespoons Cream of Tarter

1 tablespoon of Oil

Cook this ingredients until it forms an item in the pan. Pour it out onto a Tupperware lid. Cover with damp cloth. Add food coloring if you like. Store new playdough in the fridge in an airtight container. This is non-eatable playdough.

Sand Play Dough

1/2 cup sand

1/2 cup cornstarch

1/2 cup boiling water

## Sand Dollar development - From Fertilization of the Sand Dollar Egg to Zygote

Fertilization through the fourth or fifth cleavage event of a sand dollar. Watch the membrane of the Sand Dollar's egg begin to develop and then see the cells divide. How many cells are there by the end of the video?

## Sand Dollars

### We found live sand dollars on a beach in Costa Rica!

A day at the beach can be filled with amazing learning experiences. Take time to observe, spend time exploring, look for the unusual in ordinary experiences. Each day, each place you visit can be filled with wonder.

Come write about your experiences learning and teaching while vacationing in such beautiful places as Costa Rica on Wizzley, a fun and easy place to express your opinion:

## Costa Rica's Sand Dollars

I'd like to suggest that we all take a trip to a beach to Costa Rica and learn a bit of math...

145

64

153

2

29

11

30

13

## Sand Dollar Beach Day Discussion - What math have you learned at the beach?

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• fcinternetmarketing

6 years ago

Very interesting Sand Dollar"s lesson.Great lens.

• Cynthia Haltom

I spent a summer in Costa Rica learning Spanish, but I never came across live sand dollars. How exciting to see them live. Maybe next time I go I will look for them.

• ohcaroline

7 years ago

I enjoyed this sand dollar lesson. Very interesting.

• Michey LM

7 years ago

Beautiful lens and very informative for me. We have a couple of those but I have no idea that we call them sand-dollar.

• dahlia369

7 years ago

It seems to me you're the most ingenious person I know of - to turn any experience into a fun teaching lesson for kids. Congrats!! :)

• Nathalie Roy

7 years ago from France (Canadian expat)

sand dollars are one of the most interesting sea creatures

• Rhonda Albom

7 years ago from New Zealand

Wonderful information on sand dollars. We find them all the time where we live, but I never knew we could learn their age. You know what I am doing tomorrow. - Squid Angel Blessed.

• akunsquidoku

7 years ago

very interesting..:D

• Joan Haines

7 years ago

Your suggestions are wonderful. Let's all go to Costa Rica now! "Squid Angel blessed."

• bbsoulful2

7 years ago

Your lenses are always so beautiful, Evelyn - thank you!

7 years ago

So much sandy fun in learning about sand dollars :)

• fivee05 lm

7 years ago

An interesting lens!

• RuralFloridaLiving

7 years ago

Wow - very interesting lens. I've always loved sand dollars but never knew a thing about them. Thanks a lot!

• Close2Art LM

7 years ago

I wonder why they are called sand dollars? great lens, Blessed

• savateuse

7 years ago

Excellent lens!

• Mary Crowther

7 years ago from Havre de Grace

I like the play dough sand dollars, wonderful idea!

7 years ago

Sand Dollars are so beautiful and unique! Great lens.

• Renaissance Woman

What a great set of lessons. Wow. I learned so much about sand dollars. They are such favorites of mine. I've never found a live sand dollar, but do have an extensive collection of exoskeletons from when I lived on Padre Island. I can see how exciting it would be for children to experience sand dollars and all of the living lessons that they provide. Thanks for another outstanding learning presentation. Appreciated!

• cleanyoucar

7 years ago

Great information, you learn something new everyday

• xXOUTDOORSXx

7 years ago

cool lens

• lucky izan

7 years ago

it's really look like a coin, no wonder it called sand dollar

• fullofshoes

7 years ago

Once again, I am fascinated by the content of your lenses. I love to learn new things and your work is full of fun and interesting "stuff". very ~blessed~ !

• davecurrtis

7 years ago

This is a great way to learn math, nice idea.

• Stephanie Tietjen

7 years ago from Albuquerque, New Mexico

The grains of sand like to be counted. If the sand is not too fine, you can do it. I think this is a fantastic lesson, I love sand dollars, and might have loved math more with a lesson like this. Your kids are so lucky that you are their teacher.

• Ellen Gregory

7 years ago from Connecticut, USA

What an interesting lens. Beautifully done.

• slotowngal

7 years ago

Oh, I love sand dollars! We used to collect them on the beach in California when I was a girl, but I had no clue about most of the wonderful sand dollar info in your lens. Thank you so much for a beautiful look at sand dollars (and math)! angel blessed.

• rallo-smith

7 years ago

Lots of great information here. I love it when I learn new things. Thanks for sharing.

• writerkath

7 years ago

Hi Evelyn! This is a fabulous lens! Perfect teaching medium in so many ways, and for so many disciplines. Beautiful! Sometimes, when my husband &amp; I walk on the beach, we'll see a partial sand dollar and remark "Oh, look! A sand-50-cent piece" or "Just saw a Sand-Quarter!" :) I learned a lot from this lens, and thank you for taking the time to put it together. *Blessed!* :)

• Anthony Altorenna

7 years ago from Connecticut

It's always fun to search the tide pools at low tide. There's an area near our beach house where we can find sand dollars, starfish and crabs.

• intermarks

7 years ago

I have recently found a sand dollar in the beach and now only I know it is called sand dollar. This is really a beautiful natural creature.

• anonymous

7 years ago

Very informative. Thanks for sharing.

• kindoak

7 years ago

Super excellent! I remember these from my childhood abroad.

• Mary Norton

7 years ago from Ontario, Canada

I have not seen a live sand dollar. I would love to have your experience.

• SteveKaye

7 years ago

You create the most interesting lenses. Thank you for publishing this one. I found the info on Sand Dollars to be fascinating.

• MrInfopreneur

7 years ago

I had no idea what a sand dollar was till I stumbled upon your lens :)

• Lisa Morris

7 years ago

Congratulations on the purple star! This lens has a lot of great information on the sand dollar. I love sand dollars. Blessings.

• Robin S

7 years ago from USA

Like #100. Congratulations!

• amberchina

8 years ago

Sand dollars are just so stinkin' cool! Your lens has so many great ideas for parents and children to do together this summer to retain learning, so I just featured your lens on my "The Best Summer Learning Activities and Projects by Subject" lens. I know it will be helpful to even more parents and kiddos. :)

• Joanie Ruppel

8 years ago from Keller, Texas

I found some live sand dollars in the Aegean Sea off the coast of Turkey. Had to go to 8 feet deep to scoop them up in very salty water, not east to do, but worth the prize. I took one out, snapped a picture, and returned it to the sea where it belonged. Very interesting lens.

• TransplantedSoul

8 years ago

These are such beautiful animals. This lense makes me want to be on the beach right now!

• liberia88

8 years ago

It was fun exploring this page. There is a lot of great information. I would love to see live sand dollars too!! I will have to look for them when I go snorkeling on the Pacific coasts of Guanacaste, Costa Rica.

• mommy2deb

8 years ago

Interesting lens.

• Moe Wood

8 years ago from Eastern Ontario

We never learned math at the beach but I think it is a good activity to incorporate.

• Snakesmom

9 years ago

Beautiful lens! I love the sand dollars, they are so cool!

• akumar46 lm

9 years ago

What a cool Sand Dollar math lessons!Thanks.

• CherylsArt

9 years ago

What an amazing find, and such a wonderful teaching moment.

• Sharlee

9 years ago

wonderful lens! Shar

• Julia M S Pearce

9 years ago from Melbourne, Australia

Aren't they lovely.I love shells.We used to find counters on the beach as kids.

• Violin-Student

9 years ago

Great page (as usual). Thanks!

Art Haule

• ChrisDay LM

9 years ago

Great lens - home education is THE thing!

• BrickHouseFabrics

9 years ago

Wonderful lens about something that has always intrigued me!

• sorana lm

9 years ago

Evelyn your lenses are so creative and inspiring. Yet another wonderful one. Thanks

• irenemaria

9 years ago from Sweden

Sand dollar is exotic to me. But what I really loved about this is, how you and your children were standing there feeling, watching and learning about this little guy. This is exactly the way my children were raised too.

• anonymous

9 years ago

Wonderful lense of Sand Dollars! Love to be here. Thanks for creating this natural lense :)

9 years ago from East Central Florida

What a fabulous lens!

• caketech

9 years ago

I truly loved this lens! Wonderful imagery and descriptions. I didn't know how to tell the age of a sand dollar until now. Great lens! Thanks for sharing your memory.

• AUTHOR

Evelyn Saenz

10 years ago from Royalton

@myraggededge: Thank you so much and Congratulations on becoming a SquidAngel :)

• myraggededge

10 years ago

Popped back here to bless this fabulous lens :-)

• Heather Burns

10 years ago from Wexford, Ireland

amazing sand dollar lens!

• managdem

10 years ago

Nice idea to teach math at beach with sand dollars. Actually, any beach an attractive environment to enjoy anything. So, Learning with sand dollars became enjoyable.

Thanks for sharing.

• Louis Wery

10 years ago from Sarasota, Florida USA

Thank you for showing us creative ways to learn. Beautiful lens!

• kidspartythemes

10 years ago

Excellent lens! I totally agree that the more creative ways in which we can teach our kids, the more engaged they will be! 5 stars x

• AUTHOR

Evelyn Saenz

10 years ago from Royalton

@ElizabethJeanAl: Teaching on the beach in Costa Rica is an ideal classroom.

• ElizabethJeanAl

10 years ago

What an interesting and unique way to teach.

• AUTHOR

Evelyn Saenz

10 years ago from Royalton

[in reply to AndyPo] Thank you, Andy

• Andy-Po

10 years ago

Excellent lens. Great idea.

• sarita

10 years ago from Hisar

Fantastic lens... Thanks for sharing.

• Jennie Hennesay

10 years ago from Lubbock TX

What a great, indepth article on sand dollars. You are a fantastic teacher-and I'm not a child. Well maybe I'm in my second childhood.

• Frankie Kangas

10 years ago from California

Wonderful lens. I've always loved sand dollars but didn't know anything about them live. I have a collection of some. The smallest is only about 1 in across. It's pretty cool. Bear hugs, Frankie

• Terry Boroff (flipflopnana)

10 years ago from FL

All I can say is what an awesome page! I loved everything about it.

• Tom Fattes

10 years ago from Naperville, IL

Great lens on Sand Dollars. I've always been a fan but never knew you can learn so much from them.

• anonymous

10 years ago

Very thorough and beautiful lens. I especially loved the sand dollar cookies!

• Barkely

11 years ago

Thanks for adding this lens to the Fun For Kids Group:-)

• ElizabethJeanAl

11 years ago

Hi,

My name is Elizabeth Jean Allen and I am the new group leader for the Nature and the Outdoors Group.

Lizzy

• dustytoes

11 years ago

I like the idea of teaching on a beach! What fun for any child. Lensrolling to my seashell lens!

• kellywissink lm

11 years ago

5 stars!

Welcome to the group Home Schooling Support Group-Kelly

• anonymous

11 years ago

I LOVE sand dollars! Have a wonderful birthday!!!!

• AUTHOR

Evelyn Saenz

11 years ago from Royalton

[in reply to KimGiancaterino] Thank you, SquidAngel.

• KimGiancaterino

11 years ago

One of my friends made me a shadow box with a broken sand dollar and "The Legend of the Sand Dollar" poem. The delicate pieces inside the sand dollar represent peace doves. It's really beautiful. I would like to see a live sand dollar someday. Squid Angel Blessed.

• tandemonimom lm

11 years ago

Beautiful and thorough, as usual! I love the sand dollar cookie cutters. Welcome to The Homeschooling Groups!

• Susan Deppner

11 years ago from Arkansas USA

I love teachable moments, love the beach, love this lens! Another winner by Evelyn, first class all the way as always!

• Mortira

11 years ago

What a great summer activity! According to Malcolm Gladwell, summer learning is essential to a child's intellectual development. And the more fun, the better, I say!

Welcome to the Four Seasons group!

11 years ago

This is an UBER GROOVY lens. It WILL be revisited when we study invertebrates!!!!

11 years ago

Evelyn -- we've been to Costa Rica, but didn't find any sand dollars! Again, another truly remarkable and engaging lens you've masterfully created.

• Kiwisoutback

11 years ago from Massachusetts

Well done! Great photos, too. I never realized sand dollars were so mathematical, but it makes sense now that you've explained it. Squid Angel blessed!

• eclecticeducati1

11 years ago

Love this lens!! It makes me wish we lived near a beach. 5*

• Nancy Tate Hellams

11 years ago from Pendleton, SC

This is great. I love Sand Dollars but never thought about them as teaching tools. Wonderful idea and wonderful lens.

• Patricia

11 years ago

I love sanddollars. I used to collect them as a child.

• dahlia369

11 years ago

Sand dollars are magical and beautiful and so is this lens - thank you for making it and sharing it... :)

• Jimmie Quick

11 years ago from Memphis, TN, USA

Who doesn't love sand dollars. I'm sure you know of the legend of the sand dollar too. Not math related, but wonderful symbollism of the Christian faith. Of course, please add this to the Learning and Teaching Math group. I'm also going to lensroll this to my Nature Study at the Beach lens.

• motorpurrr

11 years ago

Nice of you to write about snad dollars. I had no idea they even moved, nor so many subspecies. So cool, thanx.

• Yvonne L B

11 years ago from Covington, LA

Welcome to the Naturally Native Squids group. Don't forget to add your lens link to the appropriate plexo and vote for it.

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