Doubling and halving — Mental Maths Mastery

How to do it in your head

Split, then double or halve — “work on each easy part”

1. To double: split into tens and ones, double both, add.
2. To halve: split into an even number of tens and the rest (156 = 140 + 16).
3. Halve both parts and add.

Use it for: Sharing between two, × 2 and ÷ 2, and the next two lessons (× 4, × 8, ÷ 4, ÷ 8).

Worked example: Half of 156 = 78

✏️ Practice

Work it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.

🏁 Lesson 9 test

20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.

🏅 Sign in with Google to earn the ⚖️ Double-Half Hero badge when you pass — and a certificate when you finish all 6 lessons of Part 2 · Mental multiplication & division. You can still take the test without signing in.

🖨️ Doubling and Halving Worksheet

• Worksheet set 1 (PDF)
• Worksheet set 2 (PDF)
• Worksheet set 3 (PDF)