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