128 is what percent of 640?

Question

3.4 is what percent of 5?

15 is what percent of 120?

Answer 1

Divide 128 by 640 and you get 0.2. More the decimal point two places to the right to get the percent.
120 is 20% of 640.

Now that you see how to figure this type of problem, you can do the other two. If you post your answers, we'll be glad to check them.