50 is 20% of what number
You need 20% 5 times to make 100%(20% + 20% + 20% + 20% + 20% = 100%)
Therefore, if 50 is 20% of a number, you need 5 50's to find it out.(50 + 50 + 50 + 50 + 50 = 250).
50 is 20% of 250.