The sum means the total when the numbers are added together.

Unisiting means treating groups that contain the same number of things as 'ones' or 'units'.

Add two 3-digit numbers using partitioning

Maths

In this unit pupils will add and subtract two 3-digit numbers using partitioning, adjusting, redistribution and bridging. In the future unit pupils will accurately and efficiently solve multi-step addition and subtraction problems. They will understand and explain how both addition and subtraction equations can be used to describe the same additive relationship.

In the prior unit pupils found pairs of number that composed 100 and positioned 3-digit numbers on a number line and estimated their position on unmarked number lines. They compared and ordered 3 digit numbers. In this unit pupils will add and subtract two 3-digit numbers using partitioning, adjusting, redistribution and bridging

Informal and mental strategies for adding and subtracting two 3-digit numbers

When you adjust you make a small change to a number. This is done to make a calculation easier to solve mentally.

The inverse is the opposite or reverse operation. For example, subtraction is the inverse operation of addition.

Working efficiently means finding a way to solve a problem quickly whilst also maintaining accuracy.

Add two 3-digit numbers using adjusting strategies

Redistribution is a way of transforming a sum to make it easier to calculate mentally.

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

Add 2 and 3-digit numbers by redistributing

Partitioning is the act of splitting an object or value down into smaller parts.

When you adjust you make a small change to a number. This can make a calculation easier to solve mentally.

Redistribution is where part of one addend is moved to another addend.

Choose the most efficient strategy to add two 3-digit numbers

The minuend is the number being subtracted from.

A subtrahend is a number subtracted from another.

The difference is the result after subtracting one number from another.

Partition is the act of splitting an object or value down into smaller parts.

Subtract 2 or 3-digit numbers using partitioning and bridging a multiple of 10

Subtract a pair of 2-digit numbers by finding the difference

Subtract 3-digit multiples of 10 by finding the difference between them

Choose the most efficient strategy to subtract from a 3-digit number

A bar chart uses rectangular bars to show different values.

A pictogram is a graph that uses pictures to represent information.

A table has information arranged in rows and columns.

Informal and mental strategies for adding and subtracting two 3-digit numbers

Choose a lesson (10)

These lessons will be removed by end of Summer Term 2025.