Edexcel IGCSE Maths复习笔记 1.12.2 Calculations using Bounds

Edexcel IGCSE Maths复习笔记 1.12.2 Calculations using Bounds

What are bounds?

  • Bounds are the smallest – the Lower Bound (LB) – and largest – the Upper Bound (UB) – numbers that a rounded number can lie between

How do we find bounds?

  • The basic rule is “Half Up, Half Down”
  • More formally:
    • UPPER BOUND – add on half the degree of accuracy
    • LOWER BOUND – take off half the degree of accuracy
    • ERROR INTERVAL: LB ≤ x < UB

     

Calculations using bounds

  • Find bounds before calculating and then:
    • For FRACTIONS/DIVISION:UB = UB ÷ LB and

      LB = LB ÷ UB

    • Otherwise: 

      UB = UB × UB etc.

Worked Example

转载自savemyexam

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