Four operations word problems

The idea

Word problems hide a calculation inside a story. First decide what the question is really asking, then choose the operation: combining amounts usually means add, finding what is left or the difference means subtract, equal groups mean multiply, and sharing or grouping equally means divide.

Two-step problems need two calculations — do them one at a time and write down the answer to the first step before starting the second; that number is your starting point for step two.

Key words are clues, not guarantees: 'altogether' often means add or multiply, 'each' often signals equal groups. Always finish by asking: does my answer make sense for the story (a sensible size, the right unit — cm, £, children)?

Worked example

A hall has 34 rows of 6 chairs. 18 more chairs are brought in. How many chairs are there now?

1. Step 1 — the chairs in rows are equal groups: 34 × 6.
2. 34 × 6 = 204 chairs.
3. Step 2 — 18 more are brought in, so add: 204 + 18.
4. 204 + 18 = 222.

Answer: 222 chairs

Watch out

• Stopping after the first step of a two-step problem.
• Multiplying when the groups are not equal — check the story really describes equal groups first.
• Forgetting the unit or giving a money answer with the £ and pence muddled.