To convert a fraction to a percentage, divide the numerator (top number) by the denominator (bottom number) and multiply by 100. Example: To express the fraction 2/5 as a decimal, divide 2 by 5, which equals 0.4. Multiply this by 100 for your answer: 40%.
To convert a decimal to a percentage, multiply by 100; a shortcut for this is simply to move the decimal over two places to the right. Example: 0.08 × 100 = 8%
Problem 2: If 8 out of 32 frogs in a pond have deformities, what percentage of frogs have deformities?
8/32 = 0.25 = 25%
Problem 3: In a pond, 25% of the frogs have leg deformities. If there are 100 frogs in the pond, how many have deformities?
100 × 0.25 = 25
Problem 4: If there are 68 frogs in the pond and 25% have deformities, how many have deformities? (First, make an estimate based on your answer to Problem 3—will it be a higher or lower number? This will help you decide if the answer you calculate is reasonable or whether you might need to recalculate.)
68 × 0.25 = 17