1.4.5

Limits of Accuracy

Test yourself

Rounding and Accuracy

If we round numbers then the accuracy of our calculation can change. The weight of a cooking pot to the nearest kilogram is 7kg. What is the range of possible weights of the pan?

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Upper and Lower Bounds

You need to know how to use bounds to work the higher and lower bounds of calculations with numbers that have been rounded.

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Upper and lower bounds of calculations

  • To work out the upper and lower bound of a calculation, you need to work out the upper and lower bound for each value used in a calculation.
  • You can then use these individual bounds to work out the upper and lower bounds of the calculation.
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Example - multiplication

  • You are calculating the upper and lower bounds of the area of a rectangle.
  • The height is 0.5 to 1 decimal place.
    • The height's lower bound is 0.45 and the upper bound is 0.55.
  • The length is 10 to 2 significant figures.
    • The length's lower bound is 9.5 and upper bound is 10.5.
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Example cont. - multiplication

  • The lower bound for the area is the smallest possible height × the smallest possible length.
    • I.e. 0.45 × 9.5 = 4.275
  • The upper bound for the area is the largest possible height × the largest possible length.
    • I.e. 0.55 × 10.5 = 5.775
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Example - division

  • You are calculating the upper and lower bounds of the speed = distance ÷ time.
  • A car travels 30 km to 1 significant figure.
    • The lower bound for the distance is 25 km and the upper bound is 35 km.
  • The time is 7 hours to 1 significant figure.
    • The lower bound of the time is 6.5 hours and the upper bound is 7.5 hours.
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Example cont. - division

  • The lower bound for the speed of the car is the smallest possible distance ÷ the largest possible time.
    • I.e. 25 ÷ 7.5 = 3.33 km/h
  • The upper bound for the speed of the car is the largest possible distance ÷ the smallest possible time.
    • I.e. 35 ÷ 6.5 = 5.38 km/h

Jump to other topics

1Number

1.1Using Numbers

1.2Fractions, Decimals & Percentages

1.3Powers & Roots

1.4Accuracy

2Algebra

2.1Introduction to Algebra

2.2Manipulating Algebra

2.3Proofs & Functions

2.4Straight Line Graphs

2.5Common Graphs

2.6Transformations & Tangents

2.7Properties of Graphs

2.8Solving Equations

2.9Inequalities

2.10Sequences

3Ratio

4Geometry

4.1Introduction to Geometry

4.2Triangles & Quadrilaterals

4.3Transformations

4.4Circle Basics

4.5Circle Theorems

4.6Measurements & Units

4.7Calculating Area

4.8Triangle Formulae

4.93D Shapes

4.10Vectors

5Probability

6Statistics

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