Do I have to press Enter after each answer?

No. The moment your answer is right, the next problem appears. There's no Enter key and no fade-in delay.

I'm stuck on easy problems. Are there harder levels?

Yes, and they're all open from day one. Expert gives problems like 4825 + 739 and 47 × 63. You can add negative numbers or go up to 50 problems.

Are negative numbers included?

Yes. Turn on negative numbers in the level sheet and subtraction can go below zero, like 23 − 57 = −34. Type the minus key, then the digits.

Can I change the keypad to calculator mode?

Yes. In Settings, choose phone layout (1 2 3 on top) or calculator layout (7 8 9 on top).

Can I turn off the music?

There is no music. You only hear a short tick for right and a thud for wrong, and you can turn both off in Settings.

Is it free? Are there ads?

Every mode, level and trick is free, and the app shows ads. Watch one short video in Settings to turn off full-screen ads for 24 hours.

Is it good for kids practicing arithmetic?

Yes. Easy level with the timer off works for young learners, and the times-table map shows which facts still need practice.

How long should I practice each day?

One round of Today's Challenge, 20 problems in about a minute, is enough. Do it daily and watch your 30-day trend drop. It's a quick way to keep your mind sharp.

Which multiplication tricks should I learn first?

Start with ×5, ×9 and ×11. They come up often and take about a day to feel natural.

Does the ×11 trick work for three-digit numbers?

Yes. 243 × 11 is 2, (2+4), (4+3), 3 → 2673. Insert the sum of each neighbouring pair.

How do I multiply two two-digit numbers in my head?

Split one into tens and ones: 47 × 63 = 47 × 60 + 47 × 3 = 2961.

Don't tricks slow you down at first?

For a few days, yes. After about ten problems a trick becomes automatic, and then it's faster.

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7 mental math tricks for multiplication

Multiplication gets fast in your head when you turn hard products into multiplying by 10 or 100, doubling and halving. Each of the 7 tricks below fits in one line and comes with an example you can try right now.

The tricks at a glance

Trick	Rule	Example
Two-digit × 11	Split the digits and put their sum in the middle	43 × 11 → 4 (4+3) 3 = 473
× 25	Multiply by 100, divide by 4	36 × 25 = 3600 ÷ 4 = 900
× 5	Multiply by 10, then halve	48 × 5 = 480 ÷ 2 = 240
× 4	Double twice	23 × 4 → 46 → 92
× 9	Multiply by 10, subtract once	34 × 9 = 340 − 34 = 306
Halve and double	Halve the even number, double the other	16 × 35 = 8 × 70 = 560
Squares ending in 5	First digit × (first digit + 1), then 25	35² → 3 × 4 = 12 → 1225

×11 when the middle sum is 10 or more

If the middle sum is 10 or more, carry the 1 to the left. For 78 × 11: 7, (7 + 8 = 15), 8, so the 7 becomes 8 and the answer is 858.

Why squares ending in 5 work

65² is 6 × 7 = 42 followed by 25, so 4225. It always works because (10a + 5)² = 100·a(a + 1) + 25.

Split bigger products

When no trick fits, split one number into tens and ones. 68 × 12 = 68 × 10 + 68 × 2 = 680 + 136 = 816. 47 × 63 = 47 × 60 + 47 × 3 = 2820 + 141 = 2961.

How to practice them

Learn one trick a day
Solve 10 examples without a timer
Mix them into timed multiplication at medium level (24 × 7)
Use splitting for expert level (47 × 63)

Practice with Sumbolt

Sumbolt's Tricks tab has 12 tricks, including make a ten, ×9, ×11, ×25 and squares ending in 5. Each one has three short steps, a one-line reason it works, and 10 practice problems. Then use them against the clock in multiplication & division mode.

FAQ

Which multiplication tricks should I learn first?: Start with ×5, ×9 and ×11. They come up often and take about a day to feel natural.
Does the ×11 trick work for three-digit numbers?: Yes. 243 × 11 is 2, (2+4), (4+3), 3 → 2673. Insert the sum of each neighbouring pair.
How do I multiply two two-digit numbers in my head?: Split one into tens and ones: 47 × 63 = 47 × 60 + 47 × 3 = 2961.
Don't tricks slow you down at first?: For a few days, yes. After about ten problems a trick becomes automatic, and then it's faster.

12 tricks with practice problems in Sumbolt

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