Percent Increase
Part of the Decimals, Percents & Ratios section of Coddy's Pre-Algebra journey. Lesson 34 of 56.
A ticket price goes up from 20 dollars to 25 dollars. By what percent did it rise? First find the change: 25 - 20 is 5 dollars. Then ask what percent the change is of the original price, the one you started from: (5/20) × 100 is 25. The price rose 25%.
On the board, with p for the percentage: p = ((25 - 20)/20) × 100, then p = 25. The change goes on top and the original goes underneath.
Why the original? A percent change answers 'how much bigger than before?', so it is measured against before. Dividing by the new price, 5/25, gives 20%, which is the right size of change measured from the wrong place.
Challenge
A gym membership went up from 50 dollars to 65 dollars a month. By what percent did it rise? Find the percentage p. Write p equal to the calculation, then work it out.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Decimals, Percents & Ratios
4Dividing Decimals
Dividing by a DecimalDividing by 10 and 100Dividing by a Whole NumberUnit PriceRecap: Dividing7Percent Problems
Finding the WholeDiscountsTax and TipsPercent IncreasePercent DecreaseRecap: Percent Problems