Subtract in Your Head!

Imagine you have 10 grapes. You eat 3. How many are left? You probably didn't need a pencil — you just knew! That's mental subtraction. It means working out a subtraction in your head, no writing needed. Today you'll learn tricks to make it even faster.

Subtraction means taking one number away from another. We write it with a minus sign: −. For example, 13 − 5 means 'start at 13 and take away 5'. **Strategy 1: Count Back** Start at the bigger number and count backwards by the smaller number. 13 − 5: start at 13, count back 5 steps → 12, 11, 10, 9, 8. The answer is 8. **Strategy 2: Jump to the Next Ten** If a number is close to a ten, jump to that ten first, then carry on. 32 − 7: jump from 32 back to 30 (that's 2), then jump back 5 more → 25. So 32 − 7 = 25. **Strategy 3: Use a Known Fact** You probably know that 10 − 3 = 7. Use that fact to help with bigger numbers. 50 − 30: think of it as 5 − 3 = 2, so 50 − 30 = 20. The zeros go along for the ride!