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Using estimation to check answers

Using estimation to check answers

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Summary

Using estimation to check answers

​​In a nutshell

Estimation involves finding an approximate answer for a calculation so you can have an idea that the real answer is correct. The main method of estimation is to round numbers in a calculation to make it faster and easier to perform the calculation.



Estimating

When estimating a calculation, round the numbers so they are easier to handle. Round the numbers to the first digit, then the calculation should be easier to perform. To represent an estimation, use the symbol ()(\approx) which means "approximately equal to".


Example 1

Estimate 612×11612 \times 11.


First, round 612612.


612600612 \approx 600


Then, round 1111.


111011 \approx 10


Attempt the calculation with the rounded numbers. 


600×10=6000600 \times 10 = 6000


Therefore,

621×116000.\underline{621 \times 11 \approx 6000.}


Note: You may not need to round every number in a calculation as long as you are still able to estimate a calculations.  


Example 2

Estimate 714139877141- 3987.


Round 71417141  and 39873987 using the first digit. 

71417000398740007141 \approx 7000 \\3987 \approx 4000


Estimate the answer.

70004000=30007000-4000 =3000


Therefore,

714139873000.\underline{7141-3987 \approx 3000.}​​


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FAQs - Frequently Asked Questions

How should you round numbers when estimating a calculation?

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