Finding the original quantity after a percentage increase
Sometimes you have a final amount after a percentage increase or decrease. You can use this to find the original amount.
Example
A bottle of lemonade advertises that it鈥檚 now 50% bigger. If it is now 750 ml, what was its original volume?
Answer
- Start with the original volume as 100%
- The new volume is 50% more than this: 100% + 50% = 150%
- 150% = 750 ml. We can divide by 150 to find 1%.
- 1% = 5 ml. We can now multiply by 100 to find 100%, which was the original volume.
- 100% = 500 ml
Question
After a price increase of 10% a television costs 拢495. How much did it cost originally?
Start with the original volume as 100%.
The new price is an increase of 10%
拢495 = 100% + 10% = 110%
1% = 495 梅 110 = 拢4.50
100% = 拢4.50 x 100 = 拢450
The original price of the television was 拢450.