7 Mental Math Tricks to Solve Number Puzzles Faster

May 28, 20265 min read

$Cartoon cat with round glasses in a thinking pose, a glowing lightbulb overhead and numbers and math operators swirling around its head$

Mental math is a skill, not a talent — and like any skill, a few reliable tricks plus a little daily practice go a long way. Here are seven techniques that make arithmetic faster in your head, whether you're splitting a bill, estimating on the fly, or racing the clock in a number puzzle.

1. Round to friendly numbers, then adjust

To add 47 + 28, round 28 up to 30 (47 + 30 = 77), then subtract the 2 you borrowed: 75. Working with multiples of ten and then correcting is almost always faster than column-by-column addition.

2. Break numbers apart (the distributive trick)

For 7 × 12, split the 12 into 10 + 2: (7 × 10) + (7 × 2) = 70 + 14 = 84. Decomposing one factor into a round number plus a remainder turns hard multiplication into two easy ones.

3. Multiply by working with tens

To multiply by 5, multiply by 10 and halve it (e.g., 18 × 5 = 180 ÷ 2 = 90). To multiply by 9, multiply by 10 and subtract one copy (14 × 9 = 140 − 14 = 126).

4. Subtract by counting up

For 63 − 47, don't borrow — count up from 47: +3 gets you to 50, +13 more gets you to 63, so the answer is 16. Counting up avoids carrying mistakes entirely.

5. Use squares you already know

Memorize the squares up to 15 (12² = 144, 13² = 169…). They show up constantly and let you estimate products fast — 13 × 14 is just a hair above 13² (169), so ≈ 182.

6. Estimate first, refine second

Before computing exactly, get a ballpark. Knowing 7 × 9 ≈ "low 60s" tells you instantly whether it's a good candidate for a target of 63. Estimation narrows the search before you spend effort on precision.

7. Work backward from the answer

When you have a goal number, reverse the question. Instead of combining numbers forward and hoping, ask "what would I multiply or add to reach this?" This is the single most useful habit for target-number puzzles — and it's exactly the skill Mathness trains.

The only way to get faster is reps. A single puzzle a day builds the recall that makes all seven tricks automatic. The daily Mathness puzzle is a 60-second drill that does exactly that.

Turn the tricks into instinct

Reading about mental math won't make you faster — using it will. Mathness gives you a fresh target and five numbers every round, so each of these techniques gets a workout in context. Play a few rounds and watch how much quicker the second ten feel than the first.