We all know you can add and subtract with your fingers, but if you're a little rusty on those multiplication tables, you can actually use your fingers to do easy multiplication too.
The multiplication tables from 1 to 5 are pretty easy (as are 10 and 11), but 6 through 9 can be a little bit of a challenge, especially if you need to calculate something quickly. All you do is assign the numbers 6 through 10 to each of your five fingers on each hand. Then take the two numbers you want to multiply -- in the case of the above image, 7 and 8 -- and put together the corresponding fingers (as shown in the picture to the right). Count the touching fingers, along with the fingers below them and add a zero. That's your "tens" value. Then multiply the upper portion that's above the touching fingers together (one hand x the other hand). That's your "ones" value. Add the bottom and top together and you have your answer.
It seems pretty complicated at first, but you'll get the hang of it after a few times, and it's handy if you don't have a calculator nearby. Hit the link to read more, and while you're at it, check out the other things you can do with your hands, like estimating the time of the sunset or estimate your food portions.
Tables of 6, 7, 8 and 9 in your hands [Instructables]