Estimate and check whether an answer makes sense
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The idea in everyday life
Use rounding, bounds, and an alternate check before trusting a practical calculation.
A calculator can produce a precise number even when the question or inputs are wrong.
One step at a time.
Use the sample or information you have permission to use. Keep your work as you go. You can pause between steps.
- 1
State what the answer should roughly be and identify the unit before calculating.
- 2
First estimate using rounded numbers or a range with a low and high limit. Then calculate with the exact values and compare the answers.
- 3
If the difference is large, inspect the operation, unit, decimal, timeframe, and source rather than forcing the result to fit.
See how it works.
Darius estimates that eight 8-hour shifts at $18 per hour should be near $1,150 gross (64 hours × $18 = $1,152), so he catches a formula that multiplied hours by 18 twice.
Did you cover these?
- Your work includes a three-problem reasonableness-check sheet with estimates, exact results, units, and corrections.
- Check this common mistake: Reporting many decimal places as proof of accuracy when the input was an estimate or the unit was missing.
- You can detect an implausible answer and explain which part of the setup needs review.
What to finish
A three-problem reasonableness-check sheet with estimates, exact results, units, and corrections.
Watch for this
Reporting many decimal places as proof of accuracy when the input was an estimate or the unit was missing.
How can I tell I understand it?
You can detect an implausible answer and explain which part of the setup needs review.
Quick knowledge check
Answer all 3 questions. Get at least 2 right and the lesson completes automatically.
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Answer all 3 questions above and get at least 2 right. You can review the explanations and try again.
Go to the knowledge checkOptional course overview video
Calculating Wages: The Pay-Rate-Hour Triangle
From TabletClass Math. Watch here or open it on YouTube .
Watch for an idea you can use in the practice below. You can pause or skip this optional overview.Tools, templates, and lesson sources
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