Roman has 2 red pencils in his backpack. if this is 25% of the total number of pencils, how many pencils are in his backpack?

2 = 25%. 25% also means 1/4. So, it is a quarter of something. So. So find 100%, you have to multiply 2 by 4. 2 * 4 = 8. Roman has 8 pencils in his backpack.

Total number of pencils: 8

Imagine you are adding money then, 100%= 4/4

(4 is used because there are 4 quarters in a dollar and a dollar = 100 cents )

Therefore, all you have to do is multiply 2 by 4: 2 is 25% and there are four 25 percents in one dollar

Ex: 25% + 25% + 25% + 25% = 100% 

25%=2 pencils                
50%=4 pencils 
75%=6 pencils 
100%=8 pencils in total