Quick Math

A problem shows up. Type the answer on the keypad or your keyboard. The moment your input matches the correct number, the next problem loads on its own — no submit button to hit every time. One shot per problem: if you type the full answer and it's wrong, you'll see the correct value flash, the miss gets logged in the margin, and the next problem takes over. Press ⏎ to force a check on a partial answer, or Space to skip. Subtraction answers are always positive; division always divides evenly. Use the start panel to pick which operations go in the mix and how big the numbers should get.

Speed on a drill like this is 90% fact recall and 10% tricks. The good news is that both sides improve quickly with short, focused reps. Below are the patterns that actually move the needle — the same ones traders, cashiers, and waitstaff rely on when a phone isn't an option.

How do I get faster at adding two-digit numbers?

Break each number into its tens and ones, add them separately, then combine. The schoolbook "stack and carry" method is slower in your head because you have to remember the carried digit while you're still working. Doing it left-to-right avoids that entirely.

Walk through 47 + 38:

1. Add the tens first: 40 + 30 = 70.
2. Add the ones: 7 + 8 = 15.
3. Combine the two results: 70 + 15 = 85.

That's it — three small additions, no carrying, done. Try 62 + 29: 60 + 20 = 80, then 2 + 9 = 11, then 80 + 11 = 91.

What's the trick for subtracting in your head?

Don't subtract — count UP from the smaller number to the bigger one. The answer is how far apart they are, and walking up in two easy hops is faster (and way less error-prone) than the schoolbook borrow method.

Walk through 83 − 47:

1. Start at 47. First hop: get to the nearest clean ten. 47 → 50 is a jump of +3.
2. Now you're at 50. Second hop: get to 83. 50 → 83 is a jump of +33.
3. Add the two hops together: 3 + 33 = 36. That's the distance between 47 and 83, which is the answer. So 83 − 47 = 36.

The whole point: you never subtract, you never borrow. You add two small numbers and you're done. Try 62 − 38: 38 → 40 (+2), 40 → 62 (+22), total 24. So 62 − 38 = 24.

Do I still need to memorize times tables?

Yes, through 12×12. There is no trick that substitutes for this. If 8×7 takes more than half a second, drill that single fact before anything else — on the mul-only setting, Easy difficulty, for three rounds. It will click. Every multi-digit multiplication problem later reduces to a sequence of these single facts, so a slow table is a tax on everything above it.

How do I multiply two-digit numbers without a calculator?

Split one of the numbers into a clean tens-piece plus a leftover. Multiply each piece separately. Add. Multiplying by 10 is free (just shift a zero on), so always split off the tens part first — the leftover is a single-digit multiplication you already know by heart.

Walk through 14 × 6:

1. Split 14 into 10 + 4.
2. Multiply each piece by 6: 10 × 6 = 60, and 4 × 6 = 24.
3. Add the two results: 60 + 24 = 84.

Walk through 12 × 15:

1. Split 15 into 10 + 5.
2. Multiply each piece by 12: 12 × 10 = 120, and 12 × 5 = 60.
3. Add: 120 + 60 = 180.

How do I divide quickly in my head?

Flip division into a multiplication question. Instead of asking "how many times does 8 go into 72?", ask "8 times what is 72?" — and let your times-table memory hand you the answer.

Walk through 72 ÷ 8:

1. Rephrase: 8 × ? = 72.
2. Reach for your 8-times table. 8 × 9 = 72.
3. So the ? is 9. That's the answer.

This is why the drill up top generates division as the inverse of multiplication. Every × fact you learn doubles as a ÷ fact: train 8 × 9 = 72 once, and you've also trained 72 ÷ 8 = 9 and 72 ÷ 9 = 8. Three facts for the price of one.

I have a calculator in my pocket. Why bother?

Three reasons. First, checking yourself — a calculator will happily return the wrong answer when you fat-finger an input; mental math catches typos the way a second pair of eyes catches typos. Second, reading numbers in real life — a bill, a speedometer, a sale tag, an estimate from a contractor. Fluent people sanity-check these in the time it takes to unlock a phone. Third, the cost of friction — if adding two three-digit numbers feels hard, you'll skip the math entirely and trust whatever number is put in front of you. That's the expensive habit.

How fast should I be?

On medium with all four ops at 60 seconds, a common benchmark is 40+ for "good" and 60+ for competitive. Casual target: 25. If you're under 15, don't panic — that just means one or two times-table facts haven't locked in yet. Run mul-only for three rounds on Easy, watch which pair trips you, and drill that specifically.

I know the answer but my hands are slower than my head.

Very common. Two options. First, play with the keyboard, not the mouse — digits on the number row are much faster than hunting for the on-screen keypad. Second, if you still feel like your fingers are the bottleneck, try Untimed for a few rounds just to rebuild the reflex; speed returns once the look-and-type loop stops feeling deliberate.

Related drills on Practice

Making Change stacks on top of this — fast mental addition is what makes counting change back feel automatic. Percentages is the next natural step once the four ops feel automatic: tips, discounts, and sales tax all boil down to the same multiplication and addition you're training here. Tape Measure applies that subtraction fluency to cut-list work — "27 3/8 from a 96" board" is a Quick Math problem in carpenter's clothing.

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• Mental math tricks book Arthur Benjamin's "Secrets of Mental Math" is the standard. Cheap, practical, and the techniques actually stick.
• Multiplication flash cards Times-table gaps don't fix themselves. Ten minutes a day with physical cards beats any app at this.
• Abacus The "make-a-ten" trick above is literally how abacus users think. A cheap one on your desk is a surprisingly good trainer.