First, do the division. Divide the numerator by the denominator. Then multiply by 100. To multiply a decimal number by 100, move the decimal point 2 places to the right.
Let's change 3/8 into a percent.
Do the division. 3/8 = 0.375
Now multiply 0.375 by 100. To do that, move the decimal point two places to the right. 0.375 * 100 = 37.5. That is your percent.
