L3 Use Known Number Facts to Solve Problems

Description

This Year 3 maths lesson on using known number facts to solve calculations helps pupils develop efficient mental maths strategies. Children learn how to recognise helpful number relationships such as number bonds, rounding, doubling and partitioning in order to simplify calculations that might otherwise seem difficult.

The lesson begins with a starter activity revisiting key Year 3 concepts, including addition, subtraction, place value and fractions. Pupils work through three calculations together and discuss which known facts can help them solve them mentally. The first examples use number bonds to 10 and extend these to number bonds to 100, helping pupils see how familiar facts can be applied to larger numbers. The final example focuses on subtracting 200 from 523, demonstrating how children can look first at the hundreds (500 − 200) before adding the remaining 23.

During the main teaching input, pupils are introduced to the idea of using known number facts as problem-solving strategies. The teacher models how to look carefully at each calculation and identify the most helpful approach before solving it. Examples include using number bonds to simplify addition and rounding numbers to the nearest 100 to make mental calculations easier. A number line can be used to help visualise how rounding supports efficient problem solving.

In the independent activity, pupils apply their understanding by solving a set of calculations that are difficult to complete mentally without recognising helpful number facts. Children choose an appropriate strategy, such as number bonds, partitioning, rounding or doubling, and may use equipment like base ten blocks or number lines to support their thinking. Pupils then cut and stick the calculations into their maths books, record their answers and explain the strategy they used. For example, when solving 804 − 6, pupils can partition 6 into 4 and 2 to make the subtraction easier.

The plenary activity encourages reasoning and checking. Pupils analyse the completed calculation 398 + 52 = 450 and decide whether it is true or false. They explore different ways to check the result, such as rounding 398 to 400 or recognising helpful number bonds within the calculation. By discussing multiple strategies, pupils develop a deeper understanding of flexible mental maths approaches.

Throughout the lesson, key questions prompt children to think carefully about place value, number relationships and efficient strategies. Pupils are encouraged to look for helpful number bonds, recognise when numbers are close to the next ten or hundred, and decide which step will make the calculation easier.

This resource is ideal for Year 3 maths lessons focusing on mental calculation strategies, number sense, and using known number facts to solve addition and subtraction problems. It supports pupils in developing flexible thinking and confidence when approaching more challenging calculations.