Mental math trainer

Ten problems, as fast as you can, in your head. Pick Easy for adding and subtracting, or Hard for multiplying and dividing.

47 + 38

Type the answer, then Return

Whole-number answers only

Tricks that make mental math faster

  • Add left to right. For 47 + 38, add the tens first (40 + 30 = 70), then the ones (7 + 8 = 15): 85. It’s how you’d say the number anyway.
  • Round and fix. 47 + 39 is 47 + 40 − 1 = 86. Rounding one number to a multiple of ten makes most sums one step.
  • Subtract by counting up. For 92 − 57, count from 57 to 60 (3), then to 92 (32): 35.
  • Split the bigger number when multiplying. 7 × 48 is 7 × 50 − 7 × 2 = 350 − 14 = 336.
  • Turn division into multiplication. For 168 ÷ 14, ask what times 14 is 168. Ten fourteens is 140, and two more makes 168: 12.

Why a few problems a day beats an hour once a week

Arithmetic speed is mostly recall: the more often you see 7 × 8, the less you have to work it out. Short, frequent practice keeps those facts fresh far better than a long session you rarely repeat. A round of ten takes under a minute, which is short enough to do daily.

Questions

What’s the difference between Easy and Hard?

Easy is addition and subtraction with two-digit numbers. Hard is multiplication of a two-digit number by a single digit, and division that always comes out to a whole number.

How is my time measured?

The clock starts with the first digit you type and stops when you answer the tenth problem. A wrong answer doesn’t move you on, so mistakes cost time.

Is my best time saved?

Only in this browser, on this device. Nothing is sent anywhere.

Can I practice this every day without remembering to?

That’s what SkillUnlock is for. Its Math skill shows you one problem each time you unlock, and it’s free forever.