Question

When multiplying a number by 10, move the decimal to

the right. When multiplying a number by 0.1, move the
decimal to the left. Why?

Answer 1

You can think of 0.1 as 10% (because 0.1 = 0.10 = 10%). So if you wanted to find 10% of a number, you multiply that number by 10%, or 0.1. You will notice that for any real number, the decimal point will always move 1 place to the left.

Example:

10% of 678998 = 10% × 678998

10% = 0.1, so 10% × 678998 = 0.1 × 678998

If you calculate it, you get 67899.8. And here you can see that the decimal point moved 1 place to the left. The same goes for multiplying by 10.

If 1 = 100%, then 10 = 1000%.

So, for any real number you multiply by 10, you're multiplying it by 1000%. If you do this for any real number, the decimal point will move 1 place to the right.