Rounding Answers
Solve problems which require answers to be rounded to specified degrees of accuracy
What a learner can do afterwards
- Compute a division and round the result to one decimal place as specified
- Determine the appropriate degree of accuracy for a measurement context (e.g. round to nearest penny)
- Solve a problem where an unrounded decimal answer must be interpreted in context (e.g. whole containers needed)
The lesson
When you divide, the answer often comes out as a long decimal, like 3.2857142857. Most questions do not want every digit. They ask for a certain level of accuracy, such as one decimal place, the nearest penny, or a sensible whole number.
Share 23 cups of flour equally among 7 bags. 23 divided by 7 is 3.2857142... The question asks for one decimal place, so look at the second decimal digit, which is 8. Since 8 is 5 or more, round the first decimal digit up: 3.3 cups.
To round to one decimal place, check the digit right after it. Five or more, round up. Less than five, leave the digit as it is.
Three friends split a £15.50 bill evenly. £15.50 divided by 3 is £5.1666... Money is only written to the nearest penny, so round to two decimal places: £5.17 each.
A shed holds 40 chairs per box, and 130 chairs need packing. 130 divided by 40 is 3.25 boxes. You cannot buy part of a box, so you need 4 whole boxes, even though 3.25 would usually round down to 3.
Check what the question needs, a number of decimal places, the nearest penny, or a sensible whole amount, then round to match.
Watch it
Where it sits
This opens up
Nothing builds on it yet.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.