What is the number if 80% of 50% of it is 0.72?

First find out what 0.72 is 80% of. So you would have your ratio 0.72/x = 80/100. To find out you cross multiply and divide so you would have 0.72 * 100 (72) then divide by 80 which is 0.9. To find what 0.9 is 50% of you can do the same thing or multiply 0.9 by 2 which is 1.8