KS2 SATs 2017 — Maths Paper 1: Arithmetic

The idea

Long multiplication breaks one big multiplication into two easier ones. To multiply by a two-digit number, first multiply by its ones digit, then multiply by its tens digit, and finally add the two answers together.

The key detail is the zero. When you multiply by the tens digit, you are really multiplying by a number of tens, so write a zero in the ones column of that row first. This holds the place and keeps every digit worth the right amount.

Keep each row tidy and line the digits up in columns. Before you start, estimate: round one number and multiply mentally, so you know roughly how big the answer should be. If your finished answer is nowhere near your estimate, check each row again.

Worked example

Work out 247 × 36.

1. Multiply by the ones: 247 × 6 = 1,482.
2. Multiply by the tens: 247 × 30 = 7,410. Write this row below, ending in the tens column.
3. Add the two rows: 1,482 + 7,410 = 8,892.

Answer: 8,892

Watch out

• Forgetting the zero in the ones column when multiplying by the tens digit.
• Adding the two rows before both rows are complete.