174 Speed Math for Kids
If you know that half of 10 is 5, you have done a calculation involving
fractions. You have half of your 10 fi ngers on each hand.
So what is a fraction?
A fraction is a number such as ½. Th e top number—in this case
1—is called the numerator, and the bottom number—in this case
2—is called the denominator.
Th e bottom number, the denominator, tells you how many parts
something is divided into. A football game is divided into four
parts, or quarters.
Th e top number, the numerator, tells you how many of these parts
we are working with—three-quarters of a cake, or of a game.
Writing ½ is another way of saying 1 divided by 2. Any division
problem can be expressed as a fraction: ⁄ means 6 divided by 3; ⁄
means 15 divided by 5. Even 5,217 divided by 61 can be written
as ⁄. We can say that any fraction is a problem of division.
Two-thirds (⅔ ) means 2 divided by 3.
We often have to add, subtract, multiply or divide parts of things.
Th at is another way of saying we often have to add, subtract, multiply
or divide fractions.
I am going to give you some hints to make your work with fractions
easier. (If you want to read and learn more about fractions, you can
read my book Speed Mathematics.)
Here is how we add and subtract fractions.
ADDING FRACTIONS
If we are adding quarters, the calculation is easy. One-quarter plus
one-quarter makes two-quarters, or a half. If you add another
quarter you have three-quarters. If the denominators are the same,
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