M3.2.7 For the adult
Estimate, then check
How can I tell if 389 × 52 = 20 228 is about right?
What this chapter teaches
An estimate rounds each number to one digit and works with the rounded numbers, to see whether an answer is about the right size. A division is checked by multiplying the answer by the divisor and adding the remainder.
Three questions to ask
There is no one right wording. Listen for the idea.
- How do you round 389 to one digit, and why does it go up?
- What estimate would you make for 389 × 52?
- How can you check that 7 870 ÷ 23 = 342 remainder 4?
After the chapter, the learner can
- Round to one digit to estimate 389 × 52
- Check a division by multiplying back
What they copy into their notebook
Estimate: round each number to one digit, then work it out. 389 × 52 is about 400 × 50 = 20 000. Check a division by multiplying back, then add the remainder.