Fast mental math isn't about genius: it's about shortcuts. Here are five concrete techniques that save precious time, especially useful for beating your record on GozoGozo's Mental Math mode.

1. Multiplying by 5: divide by 2 and multiply by 10

Instead of multiplying directly by 5, divide the number by 2 then add a zero (multiply by 10). Example: 48 × 5 → 48 ÷ 2 = 24 → 24 × 10 = 240. It's almost always faster than direct multiplication, especially with even numbers.

2. Multiplying by 9: multiply by 10 and subtract the number

9 × n always equals (10 × n) − n. Example: 9 × 7 → 70 − 7 = 63. This trick works for any number multiplied by 9, and avoids having to memorize the 9 times table by heart.

3. Adding by rounding first

To add two numbers like 38 + 47, round the first up to the nearest ten (40), do the simplified addition (40 + 47 = 87), then correct for the difference (87 − 2 = 85). The brain handles round tens far more easily than arbitrary two-digit numbers.

4. Subtracting using complement to 100

To subtract a number close to 100, like 100 − 37, think in complements: how much is missing from 37 to reach 100? Just take the complement to 10 of the last digit (in practice you calculate digit by digit: 9−3=6, then 10−7=3, result 63). This "complement to 9 then to 10" method is used by fast calculators for any subtraction near a power of 10.

5. Break down two-digit multiplications

For 23 × 6, break 23 into 20 + 3: (20 × 6) + (3 × 6) = 120 + 18 = 138. Multiplying by a round digit then adding the remainder is almost always faster than multiplying the whole number at once, because each step stays simple.

None of these techniques require any special talent — just a bit of practice for them to become automatic. That's exactly what the Mental Math mode lets you work on: the more you train, the more these shortcuts come naturally.