How_To_Be_Good_At_Math

110 CALCULATING •^ PARTITIONING FOR MULTIPLICATION

Partitioning for

multiplication

Just like we do for addition, subtraction, and division, we can

partition numbers in a multiplication calculation in order to make

it easier to find the answer.

To find the answer, we need

to multiply the length of the

lorry, which is 12 m, by 15.

Next, we multiply 12 by the So, the train is 180 m long.

remaining 5. The answer is

60. So, we jump up the number
    line 60 from 120 to 180.

Let’s use partitioning on a

number line to answer this

question: a lorry is 12 m long,

and a train is 15 times longer.

How long is the train?

We can partition either

number in the calculation.

Let’s partition the number 15

into 10 and 5.

First, multiply 12 by 10. The

answer is 120. So, we jump

up the number line from 0 to 120.

12 × 10 12 × 5

Partitioning on a number line

We can use a number line to break up one of

the numbers in a calculation into two smaller

numbers that are easier to work with.

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180

12 × 15 = 180

12 × 15 =?

The first jump

starts from zero 120 + 60 = 180

110_111_Partitioning_for_multiplication.indd 110 29/02/2016 18:56