I can do most percentage increase and decrease questions, but I get some wrong. Like this:
Pat buys a desk in a '15% off' sale for £57.80
I find 15% of £57.80 and add it back on. I am sure the answer is £66.47 but my teacher says this is wrong.
Please explain why.
What makes this question slightly harder is that you do not know the original price of the item.
The reduction on the item is 15% of the original price.
But you added on 15% of the reduced price instead. That is why your answer is incorrect.
The important part of solving this problem is to relate the price you were given to the original price:
|£57.80 is 85% of the original price.|
The correct answer is £68 - have a look at www.percentagecalculator.co.uk for some guidance about working out percentages.