Speed Math for Kids Achieve Their Full Potential

17 × 1 = 17

Seventeen is the numerator of the answer.
Multiply the denominators.
1 × 2 = 2
Two is the denominator of the answer.
So, the answer is 17 divided by 2, which is 8 with 1 remainder. The remainder goes to the top
(numerator), and the 2 at the bottom remains where it is for the answer. Our answer is 8½.

Dividing fractions

In the previous section we multiplied 17 by ½ to find half of 17. How would you divide 17 by ½?
Let’s assume we have 17 oranges to divide among 30 children.
If we cut each orange in half (divide by ½), we would have enough for everyone, plus some left over.
If we cut an orange in half we get 2 pieces for each orange, so we had 17 oranges but 34 orange
halves. Dividing the oranges makes the number bigger. So, to divide by one-half we can actually
multiply by 2, because we get 2 halves for each orange.
So 17/1 ÷ ½ is the same as 17/1 × 2/1.
To divide by a fraction, we turn the fraction we are dividing by upside down and make it a
multiplication. That’s not too hard!
Who said fractions are difficult?

Test yourself

Try these   problems    in  your    head:

a)  ½   ÷   ½   =

b)  1/3 ÷   ½   =

c)  2/5 ÷   ¼   =

d)  ¼   ÷   ¼   =

Here    are the answers.    How did you go?

a)  1

b)  2/3

c)  8/5 or  1   3/5

d)  1

Changing vulgar fractions to decimals

The fractions we have been dealing with are called vulgar fractions, or common fractions. To change a
vulgar fraction to a decimal is easy; you simply divide the numerator by the denominator (the top
number is divided by the bottom number).
To change ½ to a decimal you divide 1 by 2. Two won’t divide into 1, so the answer is 0 and we carry
the 1 to make 10. The decimal in the answer goes below the decimal in the number we are dividing.
Two divides into 10 exactly 5 times.
The calculation looks like this:

Here’s  another:    one-eighth  (1/8)   is  1   divided by  8.  One divided by  8   equals  0.125.

That    is  all there   is  to  it. Try a   few more    yourself.