Calculating Percentages
How to Calculate Percentage Increase
PREDICTING THE FUTURE
When we know the percentage at which a value is increasing or growing, we can calculate the value it will grow to.
Suppose your school has 320 students, but studies show that the school-age population in your neighborhood will increase by 15% next year. How can you use this information to predict the number of students next year?
STEP 1: PERCENT TO DECIMAL
Convert the percentage to a decimal. You can do this by dividing the number by 100.
In this example, you'll end up with the decimal number 0.15.
STEP 2: MULTIPLY
Multiply this number times the original value.
This gives us 48.
STEP 3: ADD
If you are simply looking for the number of new students, your answer will be 48 students. However, if you want to find the new total, you will have to add the increase (48 students) to the original value (320 students).
increased value will be 368 students, which is 15% more than 320 students
HUGE INCREASES
Some values can increase more than 100%, meaning they more than double. In these situations, the same steps still apply. Here's what the steps look like for a collector's card that began at $7 but increased in value 250%.
Step 1: 250 ÷ 100 = 2.5
Step 2: 2.5 x 7 = 17.5
Step 3: 7 + 17.5 = 24.5
The card is now worth $24.50!