Brain Training · Intermediate

Mental maths strategies: rounding, doubling and partitioning tricks

Mental maths is working out answers in your head using shortcuts. Rather than picturing a written method, you change the numbers into friendlier ones that are easy to work with.

Ages
9+ (rough guide)
Level
Intermediate
Subject
Brain Training
Time
10–15 minutes
Format
Online + printable
Try it online Print worksheet & answers Online + Print
  1. 1Learn it
  2. 2See it worked
  3. 3Try it online
  4. 4Print it
  5. 5Check your answer

Before you start

Who it's for and what to know first

Times tables to 10 × 10 and adding two-digit numbers.

Learn it

How it works

  • Round and adjust: 49 + 36 = 50 + 36 − 1 = 85. 99 × 7 = 100 × 7 − 7 = 693.
  • Double and halve: halve one number and double the other. 25 × 16 = 50 × 8 = 100 × 4 = 400.
  • Partition: split into tens and ones. 15 × 12 = 15 × 10 + 15 × 2 = 150 + 30 = 180.
  • Counting on for subtraction: 402 − 198 — from 198 to 200 is 2, 200 to 402 is 202; total 204.
  • Subtracting from 1,000: make each digit add to 9 except the last, which adds to 10. 1,000 − 367 = 633.

Worked example 1

5 × 48

  1. 5 is half of 10.
  2. 48 × 10 = 480.
  3. Halve it: 240.

Answer: 240

Try it online · print it · check it

Practice questions

Work it out in your head, then type the answer. Type your answer, then press Check answers.

Tips

Common mistakes

  • Adjusting the wrong way after rounding (49 + 36 → 50 + 36 + 1).
  • Trying to hold too many steps — write down a middle answer if you need to.

Where next?

Harder / next skillLogic grid puzzlesIn a logic grid puzzle you use clues to match items — people, pets, colours — without guessing.RelatedNumber sequencesA sequence is a list of numbers that follows a rule.RelatedLong divisionLong division is a written method for dividing a large number by a number with two or more digits (or by a single digit when you want to show every step).RelatedMultiplication chartA multiplication chart (times table grid) shows every product from 1 × 1 to 12 × 12.MoreAll Brain Training resourcesPuzzles that exercise reasoning rather than general knowledge.

Last reviewed: 25 September 2026