Math Expressions. How to write simple mathematical expressions.
When writing down expressions in algebra you need to write them down in a specific way. In algebra a letter can be used to stand for an unknown quantity. Adding and taking away are straightforward:
x+7 means x add 7
x -7 means x take away 7
but times and divide can be harder to do:
7x mean 7 times x
x/7 means x ÷ 7
Let’s have a look at a real life example.
A fish pod contains a large amount of fish. Write down an expression if:
a) 1 more fish is added to the pond
b) 2 fish are taken out of the pond
c) 3 times the original amount of fish are added to the pond
d) the amount of fish in the pond is divided by 4
First of all use the letter f to stand for the amount of fish originally in the pond.
a) f + 1 since there are no special rules for adding.
b) f – 2 since there are no special rules for taking away.
c) 3f since if you are multiplying the number comes first and the letter comes second.
d) f/4 since you always write a division as a fraction (with a line).
A line has a length of y cm. Write down an expression if the length of the line is trebled.
Here we are multiplying the length of the line by 3.
So y×3 times by 3 can be written as 3y.
Another line has a length of z cm. Write down an expression if the length of the line is halved.
Halving is the same as dividing by 2.
so Z ÷divided by 2 can be written as z/2.
Just remember when you are multiplying put the number first followed by the letter, and leave out the multiply sign.
Use a line for dividing.