Brainlag PlusWork back to the original amount after a percentage change, take VAT off, combine two changes and compare deals.
Work backwards with the multiplier
After a 20% discount, a price is 80% of the original.
So divide by 0.8, do not add 20% back.
- sale price £36 after 20% off
- £36 is 80% of the original
- original = £36 ÷ 0.8 = £45
Check: 20% of £45 is £9, and £45 − £9 = £36. Adding 20% of £36 gives £43.20, which is wrong, because the 20% was of the original.
Prices with VAT at 20% are 120% of the price without: divide by 1.2.
The rest of this lesson and its 7 practice questions are in Plus.
Screen 1 of 3, free to read.
- 7 exam-style questions, marked as you go, each with a worked solution
- The Scientific Calculator beside every question
- Anything you get wrong is saved to your flashcards