Finding the Percent of a Number
To determine the percent of a number do the following steps:
- Multiply the number by the percent (e.g. 87 * 68 = 5916)
- Divide the answer by 100 (Move decimal point two places to the left) (e.g. 5916/100 = 59.16)
- Round to the desired precision (e.g. 59.16 rounded to the nearest whole number = 59)
How to Calculate Percentages
There are many formulas for percentage problems. You can think of the most basic as X/Y = P x 100. The formulas below are all mathematical variations of this formula.
Let’s explore the three basic percentage problems. X and Y are numbers and P is the percentage:
- Find P percent of X
- Find what percent of X is Y
- Find X if P percent of it is Y
Find Percent of Two numbers example: You need to find out what percent is 7 out of 300, enter 7 in the first field and 300 in the second field. Answer: 2.33%. Solution: First divide low number by high: 7/300 = 0.023 Second: multiply the result by 100. 0.023*100 = 2.33% Answer: 2.33%
Another example, suppose you have 25 test scores, and in order from lowest to highest they look like this: 43, 54, 56, 61, 62, 66, 68, 69, 69, 70, 71, 72, 77, 78, 79, 85, 87, 88, 89, 93, 95, 96, 98, 99, 99. To find the 90th percentile for these (ordered) scores, start by multiplying 90% times the total number of scores, which gives 90% ∗ 25 = 0.90 ∗ 25 = 22.5 (the index). Rounding up to the nearest whole number, you get 23.
Counting from left to right (from the smallest to the largest value in the data set), you go until you find the 23rd value in the dataset. That value is 98, and it’s the 90th percentile for this data set.
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