Edexcel IGCSE Maths复习笔记 1.8.1 Reverse Percentages

What is a reverse percentage?

• A reverse percentage question is one where we are given the value after a percentage increase or decrease and asked to find the value before the change

How to do reverse percentage questions

• You should do these in exactly the same way as percentage increase & decrease questions!
• Identify “before” & “after” quantities
• FIND percentage we want:
  • Increase – ADD percentage to 100
  • Decrease – SUBTRACT from 100

   

• Write down a STATEMENT connecting “before” and “after”:
  • “after is a percentage of before”

   

• Write down the statement as an EQUATION using decimal equivalent
  • remember “is” means “=”

   

• SUBSTITUTE and SOLVE

Worked Example

转载自savemyexam