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Using estimation to check answers

Using estimation to check answers

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Explainer Video

Tutor: Labib

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 11612×11.


First, round 612612612.


612≈600612 \approx 600612≈600​


Then, round 111111.


11≈1011 \approx 1011≈10​


Attempt the calculation with the rounded numbers. 


​600×10=6000600 \times 10 = 6000600×10=6000​


Therefore,

621×11≈6000.‾\underline{621 \times 11 \approx 6000.}621×11≈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 7141−39877141- 39877141−3987.


Round 71417141 7141 and 398739873987 using the first digit. 

​

7141≈70003987≈40007141 \approx 7000 \\3987 \approx 40007141≈70003987≈4000


Estimate the answer.

​

​7000−4000=30007000-4000 =3000 7000−4000=3000


Therefore,

​7141−3987≈3000.‾\underline{7141-3987 \approx 3000.}7141−3987≈3000.​​​


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Learn with Basics

Learn the basics with theory units and practise what you learned with exercise sets!
Length:
Numbers to 1000

Unit 1

Numbers to 1000

Rounding to the nearest 10, 100 and 1000

Unit 2

Rounding to the nearest 10, 100 and 1000

Jump Ahead

Score 80% to jump directly to the final unit.

Optional

Using estimation to check answers

Unit 3

Using estimation to check answers

Final Test

Test reviewing all units to claim a reward planet.

Create an account to complete the exercises

FAQs - Frequently Asked Questions

How should you round numbers when estimating a calculation?

Numbers can be rounded when estimating a calculation. Round the numbers in the calculation to the first digit. E.g. To find 713 x 62, round 713 to 700 and round 62 to 60.

What is the purpose of estimation?

Estimation involves finding an approximate answer for a calculation so you can have an idea that the real answer is correct.

How do you estimate numbers?

The main method of estimation is to round numbers in a calculation to make it easy to answer.

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