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

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