Being efficient means finding a way to solve a problem quickly whilst also maintaining accuracy.

A mental strategy is a method chosen to find something out which can be done in your head or with some jottings.

The process of unitising and exchanging between place values is known as regrouping.

Make efficient use of subtraction strategies including column subtraction

Maths

In this unit pupils will identify the minuend and the subtrahend in column subtraction and explain the column subtraction algorithm They will subtract from a 2-digit number using column subtraction with exchanging In the future unit pupils will use their knowledge of column addition column subtraction with exchanging to solve problems They will evaluate the efficiency of strategies for subtraction

In the prior unit pupils identified the addends and the sum in column addition. They used their knowledge of place value to correctly lay out column addition. In this unit pupils will identify the minuend and the subtrahend in column subtraction and explain the column subtraction algorithm. They will subtract from a 2-digit number using column subtraction with exchanging.

Column subtraction

Which calculations would it be most efficient to answer using a mental strategy? 

Which calculations would it be most efficient to answer using column subtraction? 

Sam calculates 401− 396 by counting on from 396  He found a difference of {{ }}. 

Aisha wants to calculate 827 − 299  How should she calculate this using a mental strategy? 

Where is regrouping needed in the column subtraction? 

Finish the column subtraction. What is the difference?

Complete the column subtraction. What is the difference?

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