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.

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

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

Maths

Add two 3-digit numbers using partitioning

Add two 3-digit numbers using adjusting strategies

Add 2 and 3-digit numbers by redistributing

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

Use addition and subtraction to solve problems involving bar charts, pictograms and tables

Use addition and subtraction to solve problems in different contexts

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

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

102 + 130 = 232 is calculated using partitioning, adjustment or redistribution and represented using base ten. Which of the three methods is shown?

Which of these two words describes how a solution is found 'efficiently'?

Which method would be best for solving 507 + 260?

Match the equations with the method which was most efficient for finding the sum.

Each bundle contains ten straws. How many straws are there altogether?

Fill in the missing number in this sequence: 70, 80, 90, 100, {{ }}, 120, 130, 140

Fill in the missing number in this sequence: 170, 175, 180, 185, {{ }}, 195, 200, 205

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

Lesson outcome