What's an easy way to multiple big numbers by 5?

Question

To multiply any number by 5, you just divide the number by 2 (cut it in half), then multiply by 10 (add a zero to the end). Numbers greater than 12 tend to get harder and harder. So, here's an example. What is 68 x 5?

First, divide 68 by 2 and you get 34. Now multiply by 10 (add a zero to 34). The answer is: 340.

Answer 1

To multiply any number by 5, you just divide the number by 2 (cut it in half), then multiply by 10 (add a zero to the end). Numbers greater than 12 tend to get harder and harder. So, here's an example. What is 68 x 5?

First, divide 68 by 2 and you get 34. Now multiply by 10 (add a zero to 34). The answer is: 340.

For ODD WHOLE numbers, you can also apply this rule: Subtract 1 from the number, divide by 2, then add a 5 to the end. For example, in 47 x 5 (47-1=46; 46/2=23, place a 5 at end; answer 235) Odd numbers multiplied by 5 always end in 5.