Partitioning for subtraction

Partitioning for

subtraction

Subtracting numbers is often simpler if you split them into

numbers that are easier to work with and then subtract them

in stages. This is called partitioning. We usually partition just

the number being subtracted.

First, we subtract the tens

from 81: 81 − 20 = 61

Next, we subtract the ones from

the remaining 61: 61 − 5 = 56

By splitting the calculation into two easy

steps, we’ve found that: 81 − 25 = 56

Let’s subtract 25 from 81 by

partitioning the number 25.

To help with the tricky numbers, we can

put the numbers on a grid and label the

columns to show their place values.

81 − 25 =?

T O T O T O

Partitioning practice

There were 463 flowers in the

field, and Tessa picked 86 of

the flowers. How many were

left in the field?

Answer on page 319

TRY IT OUT

To work out the

answer, we can

do a subtraction

calculation.

There were 463

flowers and 86

were taken away, so

the calculation you

need to do is: 463 − 86

Try partitioning

the number 86

into tens and ones,

and subtract it in

stages from 463.

81 − (^25) = ??
81 20 61
61 5 56
−
−

=
81 − 25 = 56
T O T O T O
T O T O T O
090_091_Subtraction_facts_Partitioning_for_subtraction.indd 91 29/02/2016 18:56