Estimates on one side of the answer
Show on a big screenA school collects ₹2,31,400 in term one and ₹4,67,850 in term two. Is the total more than 6 lakh?
- Two amounts to add.
- Round both down: 2,00,000 + 4,00,000 = 6,00,000. The total is more.
- Round both up: 3,00,000 + 5,00,000 = 8,00,000. The total is less.
- The total sits between 6 lakh and 8 lakh.
Yes. Rounding both amounts down to the lakh gives 6 lakh. The real total is more.
The rule
An estimate is an answer found with rounded numbers. The sum is the answer to an add. The difference is the answer to a take-away.
Rounding down never makes a number bigger. Rounding up never makes a number smaller. So we know which side of the answer the estimate is.
Round both numbers down: the estimate is never more than the sum. Round both up: it is never less than the sum. For a difference, round the first down and the second up. The estimate is never more than the difference.
| Job | Round | Estimate | The answer is |
|---|---|---|---|
| 7,82,300 − 3,15,200 | First down, second up | 3,00,000 | More than that |
| 7,82,300 − 3,15,200 | First up, second down | 5,00,000 | Less than that |
Round one up and one down. The estimate can be on either side.
Round each number up or down in the lab. See which side the estimate lands.
Loading lab…
Try the lab to finish this lesson.