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​​In a nutshell

Estimation means finding an approximate answer to a calculation. Estimating involves rounding numbers to 11 or 22 significant figures before performing a calculation. The estimated answer would be close to the actual answer. ​

Estimation in calculations

Round the numbers in the calculation to 11 or 22​ significant figures before performing the calculation to find an approximate answer.​

Example 1

Estimate the value of  67.9+2.1614.4\dfrac{67.9+2.16}{14.4}.

First, round all 33 numbers to an appropriate number of significant figures:

67.96867.9 \mapsto 68

2.1622.16 \mapsto 2

14.41414.4 \mapsto 14​​​​

Carry out the calculation with the rounded numbers:

67.9+2.1614.468+214=7014=5\dfrac{67.9+2.16}{14.4}\approx \dfrac{68+2}{14} = \dfrac{70}{14} = 5

67.9+2.1614.45\underline{\dfrac{67.9+2.16}{14.4} \approx 5}​​

Estimation with square roots

Square roots can be estimated by identifying square numbers near a number.

Example 2

Estimate the value of 74\sqrt{74} to 1 d.p.1\space d.p.

7474 is inbetween the square numbers 6464 and 8181

64=881=9\sqrt {64} = 8 \\\sqrt {81}= 9

7474 is closer to 8181 than 6464.

Therefore, 748.7\underline{\sqrt{74} \approx 8.7}​​


Want to find out more? Check out these other lessons!

Rounding errors and estimating

Frequently Asked Questions (FAQ)


  • Question: What is estimation?

    Answer: Estimation means finding an approximate answer to a calculation.

  • Question: How do you find the estimate for square roots?

    Answer: Estimates for square roots can be found by identifying the position of numbers between consecutive square numbers.

  • Question: How do you estimate calculations?

    Answer: Round the numbers to an appropriate number of significant figures, then calculate with these numbers.



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