Number · Challenge 7 of 25 · about 6 min
Check the Shopping Estimate
Compare a friendly-number estimate with an exact shopping total.
Your challenge
Take your time. Your answer is checked only when you choose Check Answer.
Curriculum details
- Curriculum code
- VC2M4N07
- Strand
- Number
- Focus
- Use rounding and estimation to judge whether a calculation is reasonable.
Interactive visual
An interactive Round, then check exactly model is ready. Choose Show Visual Trick to reveal and hear one mathematical change at a time.
Visual Trick
Round, then check exactly
Compare the distances to the neighbouring multiples of $10, then calculate exactly.
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Step 1
Round to the nearest $10: $47.80 is $2.20 from $50, and $29.95 is $0.05 from $30.
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Step 2
Add the friendly amounts to estimate $80.
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Step 3
Add the exact dollars and cents to get $77.75.
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Step 4
Place $77.75 close to $80 on a number line.
Your answer
Worked explanation
Why the answer makes sense
- To the nearest $10, $47.80 rounds to $50 because the distances are $2.20 to $50 and $7.80 to $40. Likewise, $29.95 rounds to $30 because the distances are $0.05 to $30 and $9.95 to $20.
- $47.80 + $29.95 = $77.75.
- $77.75 is $2.25 from $80, so Mia’s estimate is reasonable.
This counts as one completed curriculum item. You can replay the model or review it again anytime.