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For multiplication, just break it down into small bits in pieces, especially easy numbers like 2, 3, 5, 10, and 12. And then just multiply those instead. If needed, you can also use this: ac + bc = c(a+b)

For example, 12 * 320 = 12 * 4 * 8 * 10, which is 48 * 8 * 10. Okay now, you have to multiply 48 and 8! Then you break that down. 48 * 8 = (40 * 8) + (8 * 8).

That is 320 + 64, or 384. Then multiply that by 10. You get 3840! It may take some practice, but when you succeed, you will be amazing!

I have to say, pretty much the same for division.

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Q: How can you multiply and divide in your head without using a calculator?
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