To calculate percentages on a calculator, divide the part by the whole and then multiply the answer by 100. For example, to find what percent of 80 is 20, divide 20 by 80. The result is 0.25, then multiply 0.25 by 100 which equals 25 percent.
To find the percent of a number, divide the percent by 100 and multiply the result by the whole. For example, to find 35 percent of 150, 35 divided by 100 equals 0.35 and 0.35 times 150 equals 52.5.
To find the whole when given the percent and the part, divide the percent by 100 and divide the part by the result. For example, to find 50 is 25 percent of what number, divide 25 percent by 100 which equals 0.25, then divide 50 by 0.25 which equals 200.