1.7.4

Upper Lower Bounds

Test yourself

Upper and Lower Bounds

When we estimate answers, we will either overestimate or underestimate the correct answers. These estimations can give us a range which the correct answer must be within.

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What is 5.43 & times 12?

  • This multiplication is hard to work out, but we can find a range for the answer by rounding 5.43.
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Upper bound

  • If we round 5.43 up to the nearest whole number, we will overestimate the answer.
    • We know that the real answer is less than this overestimate so we can write (5.43 × 12) < 72.
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Lower bound

  • If we round 5.43 down to the nearest whole number we will underestimate the answer.
    • We know that the real answer is more than this overestimate so we can write 60 < (5.43 × 12).
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Inequality

  • From these estimations we know that 5.43 &times 12 is more than 60 and less than 72.
    • We can write this using the double inequality: 60 < (5.43 × 12) < 72.

Jump to other topics

1Number

1.1Place Value

1.2Factors & Multiples

1.3Operations

1.4Fractions, Decimals & Percentages

1.5Growth & Decay

1.6Measurements & Units

1.7Accuracy

2Algebra

3Ratio, Proportion & Rates of Change

4Geometry & Measures

5Probability

6Statistics

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