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5 interesting Brain teasures

Updated on July 15, 2013

Why puzzles ?

In recent times whether you get to enter some higher studies collages or some company for job. The major criteria they usually consider to select their best candidates is through an aptitude test. Most of the organisations ask the Brain teasing questions at Interviews, There your IQ and your speed of response matter a lot.

For few are born with god gifted talents in some special field, others can perform well in any field in accordance with their IQ. And the best way to improve your IQ is Practice.

"Practice is solution to millions of problems". The more you practice, better you gonna improve.

Congrats, for here your start or next level of practice. 5 interesting brain puzzles presented below may be based on some Mathematical reasoning or just some logical IQ which could be wonderful food for your mind. So, Lets start with our Puzzles.

Best would be if you try these without looking at solutions, and refer solutions only if you need it after a try.

The 3 Switches

Puzzle #1

There are 3 switches numbered 1,2 and 3, in a room 'A', one among which if turned 'ON' lights a 100 watt bulb in another room 'B'. Other two switches have no connections to any load. A person is sitting in room 'A' and allowed to leave room 'A' and enter the room 'B' just ones, providing any combinations of 'ON' or 'OFF' to the switches.

What is the cent percent probable way to determine the right switch to turn the bulb 'ON' with his single attempt to enter the room 'B'?

There is no way for light escaping from room 'B' to reach the person in room 'A', he needs to get inside the room. And also Switchboard can't be opened, its sealed to wall.


If the person tries to simply hit guess by turning on any one switch, it may turn out to be the wrong one. He'll still have two options to guess from. So, it isn't the cent percent probable idea. Since, the simple trick of checking through 'on' and 'off' method is not helpful with any combinations; It simply means there lies some other trick to get to the solution.

So, reading the question again we find a clue that the load is a 100 watt light bulb.

The idea is to turn 'On' a switch say switch no. '1' for ten minutes, now turn it 'off' and turn 'On' the another switch no. '2', now if the person enters room 'B'.

If the bulb is now glowing that means correct switch is, switch no. '2'. If bulb isn't glowing that means either '1' or '3' is the right switch. Since it is a 100 watt bulb, it means the bulb should be heated up after glowing for 10 minutes. Now that gets us to our answer, touch the bulb softly if it feels hot simply means the correct switch was 'Switch no. 1', and if it is cold 'switch no. 3' is the right one.

Magical Tank

Puzzle #2

At the center of e dense forest there is a big bungalow, behind the bungalow there lies a giant steel tank. The tank is magical. whatever fells in that magic tank grows very rapidly in quantity, forming more identical substances.

On January 1st a flower fell into the tank, on January 2nd there were two flowers, 4 on January 3rd, 8 on 4th and the population grew to 32 on January 6th. If this tank of Volume 100 cubic meter fills half in 15 days, how many days will it take for the tank to be filled completely with flowers?

Solution :

It is a very simple mathematics cum logic based question, and can easily reach to correct solution if you apply a little brain.

Watch out the series of increment of flowers in tank:

  • Day 1 - Only 1 flower
  • Day 2 - There are 2 flowers.
  • Day 3 - 4 flowers
  • Day 4 - 8 flowers
  • Day 5 -
  • Day 6 - 32 flowers

If we keenly observe the series and the missing value, we find that the value doubles every next day. Thus if tank fills half the volume in 15 days with say 'x' no. of flowers, the very next day no. of flowers will just double to occupy twice the recent volume.
Hence, the correct answer would be, it will take 16 days for entire volume of tank to be filled with flowers.

Ronney's Challenge

Puzzle #3

Ronney's uncle has come to visit Ronney on his birthday, after the party is over at 11 p.m. Ronney wasn't interested to sleep, he wanted to spend some time with Uncle Tang. Uncle Tang provides Ronney with lots of interesting challenges and puzzles, he likes his Company.

Today's challenge provided to Ronney by Uncle Tang is like-

He gave Ronney 2 Conical flasks of Capacity 300 ml and 700 ml each, and 3 beakers each of capacity 1500 ml. Also a tub filled with water.

Than Uncle Tang asked Ronney to fill the beaker 1 with 1200 ml of water, beaker 2 with 400 ml, and beaker 3 with 100 ml of water, using flasks as only measuring instruments.

Do you have some idea how would Ronney accomplish it? For flasks are of different capacity from measured quantity we want.

Solution :

The very first thing to be considered with such questions is one should not loose the patience and ignore the question just by seeing lots of numbers at once. If the question is clearly examined with patience on a step by step basis, one may easily proceed to solve for the answer.

So the answer goes like- Ronney first fills the 700 ml flask with water, and carefully tranfers its content to 300 ml flask. Once the smaller flask is completely filled to its volume, the remaining quantity in larger flask is offcourse 400 ml of water. Now, he transfers the contents of larger flask to beaker no. 2, one step is now accomplished.

Now, moving towards second step- Ronney again fills 700 ml flask with water from tub, and just like above he transfers 300 ml from it to smaller flask, he than drops back the content of smaller flask in tub and refills the empty smaller flask with water from larger flast. Now, that 600 ml of water have been removed from the larger flask of 700 ml capacity, only 100 ml is remaining in it. Ronney pours the remaining 100 ml water in beaker 3, so, the second level is accomplished as well.

Next moving towards the third step, Ronney fills the leftout beaker to its entire capacity of 1500 ml, now he removes 300 ml out of it through smaller flask and pours it back in tub. Now, the remaining amount in beaker 1 is 1200ml of water. i.e. the entire task is accomplished and challenge is successfully met. :)

Frog in well

Puzzle #4

At the back of Sunny's yard, there is a very old abandoned well. Once a frog passing by the well fells inside it.

The depth of well is 10 meters, and is filled with water up to 3 meters from bottom, its wall have turned slippery due to algae growth.

The frog takes a 40 cm high hop in one second, and slips back 20 cm after every two hops. He swims upward at a rate of 50 cm/s. What is the total time taken taken by the frog to reach at the top of well ?

Solution :

Here Since the first 3 meters is filled with water. So total time taken by frog would be sum of time taken to swim upward and time taken to hop till top.

Time taken to swim upward would be calculated as:

Taking Rate of upward swim as 50 cm per second

=> In one second frog moves : 50 cm

=> To move up by 1 cm it will take : 1/50 seconds

=> To move by 3m i.e. 300cm, it will take : 300 x (1/50) seconds

i.e. 6 seconds

Now time taken to hop up through wall is calculated as :

height of wall = 7 m i.e. 700 cm

The frog will hop 40 cm in one second, and slips by 20 cm at every 3rd step

i.e. it's rate of moving upward can be calculated as (40+40-20) cm per 3 second

i.e. 60 cm per 3 second or 20 cm per second

hence, frog will move to height 700 cm in '700/20 seconds' or '35 seconds'

therefore, total time taken by frog to move to the horizon is 6 s +35 s = 41 seconds

Puzzle #5

Mr. Dutta has extremely busy schedule these days, with just a total of 3 hours a day for self. He spends an hour of it in his hobby cooking, and remaining time period in blogging.

He generally reads a blog in 10 minutes, and can write a niche content blog in 20 minutes (Ignoring the size and content of the blog). If Mr. Dutta credits himself for reading a blog with '5 points' and for writing a blog with '10 points'. What is the maximum credit point he can gain a day ?


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