### 33 Answers

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- roderick_youngLv 71 month ago
Most math expressions, including "12 * 13 =" can simply be typed into Google for an answer.

It there is no computer on hand, and you don't know how to use pencil and paper, or don't have any on hand, here is the trick for multiplying teen numbers in your head:

Take the 1's digit of the second number, and add it to the first number. The 1's digit of 13 is 3. 12+3 = 15. Shift that number over by 1 place, to get 150. Finally, multiply the two 1's digits of the numbers together, and add it to the result. The 1's digits are 2 and 3. 2 x 3 = 6. 150 + 6 = 156 (answer).

Another example: 12 * 17 = ?

12 + 7 = 19.

190

2 * 7 = 14

190 + 14 = 204 answer.

- BrianLv 61 month ago
So, you have a phone/computer with a calculator function, and don't know how to use it.

You'll go far in this world.

Yes, it only works for "teens," but 11 and 12 are included, too.