We can say that 20 students represent 100 % and that 4 students represent x % of all students. Then we can use the proportion: 20 : 4 = 100 : x, or 20 / 4 = 100 / x. Then we will cross multiply: 20 x = 4 * 100, 20 x = 400, x = 400 : 20 , x = 20 %. Also we can say that 4 = 1/5 * 20 and 1/5 * 100 = 20 % Answer: 4 students is 20 % of 20 students. Hope this helps. Let me know if you need additional help!