How_To_Be_Good_At_Math

138 CALCULATING •^ PARTITIONING FOR DIVISION

Partitioning for division

When you’re dividing a number with two or more digits, it helps to

break that number down, or partition it, into smaller numbers that

are easier to work with.

Let’s divide 147 by 7 using

partitioning.

We’re going to partition

147 into 140 and 7.

First, we divide 140 by 7. We

know from the multiplication

table for 7 that 7 × 10 = 70, so

7 × 20 = 140. This tells us that

140 ÷ 7 = 20

Now we divide 7 by 7. That’s

easy! The answer is 1.

Now we simply add up

the answers we got

from dividing the parts

separately: 20 + 1 = 21

So, 147 ÷ 7 = 21

Add up the two

quotients to give

you the answer

Break up 147

into easy-to-

divide parts

Divide the two

parts separately

147 ÷ 7 = 21

147 ÷ 7 =?

How to partition

The first step in partitioning for division is to break the number we’re dividing

(the dividend) into two smaller numbers. It’s often a good idea to break the

dividend into a multiple of 10 and another number. Then we divide each

of these two numbers by the number we’re dividing by (the divisor).

Finally, we add our two answers (or quotients) to get the final answer.

147

140

140 ÷ 7 = 20

7

7 ÷ 7 = 1

20 + 1 = 21

7

140

138_139_Partitioning_for_division.indd 138 29/02/2016 18:03