Explain how adjusting the subtrahend affects the difference: partitioning

Maths

In this unit pupils will explain how increasing or decreasing the minuend affects the difference and solve subtraction calculations mentally using known facts explaining how adjusting the minuend can make mental calculation easier In the future unit pupils will explain how to balance equations with addition or subtraction expressions and use their knowledge of balancing equations to solve problems

In the prior unit pupils used the concept of same sum to simplify and solve addition problems  In this unit pupils will explain how increasing or decreasing the minuend affects the difference and solve subtraction calculations mentally by using known facts explaining how adjusting the minuend can make mental calculation easier

Use equivalence and compensation to simplify and solve subtraction problems

Look at the image of the counters. What is being referred to by the question mark?

True or false? If the minuend stays the same and the subtrahend decreases then the minuend and subtrahend will be further apart on a number line.

Look at the jottings. Which word would you use to complete the following sentence?
I’ve kept the minuend the same and subtracted 15 from the subtrahend so I had to {{ }} 15 to the difference

Look at the jottings. Which same number works in both gaps in this sentence?
I’ve kept the minuend the same and added {{ }} to the subtrahend so I had to subtract ___ from the difference.

Look at the jottings. What was the value of the adjustment to the subtrahend and the difference?

Which number in the final equation shown is incorrect?

If the difference is 19, which part of the bar model below is the subtrahend?

Solve the following calculation mentally by adjusting the minuend and subtrahend.
456 − 42 = {{ }}

Solve the following calculation mentally using unitisation.
{{ }} = 890 − 540

Solve the following calculation mentally by adjusting the minuend and then the difference.
3,005 − 1,200 = {{ }}

Solve the following calculation using a mental strategy.
{{ }} = 903 − 46

Without calculating the value of each expression can you work out which symbol should go between these two expressions?
8.04 − 2.3  {{ }} 8.04 − 3.2

This lesson will soon be taken down.

Explain how adjusting the subtrahend affects the difference: partitioning

Lesson outcome