Decimal place value (age 9+)
Round decimals with two decimal places to the nearest whole number and to one decimal place
What a learner can do afterwards
- Round 3.47 to the nearest whole number (3) and to 1 d.p. (3.5)
- Round 12.95 to 1 d.p. (13.0) and explain the boundary case
- Estimate 4.83 + 2.17 by rounding each to the nearest whole number
The lesson
To round a decimal to the nearest whole number, look at the tenths digit. That is the first digit after the decimal point. If it is 5 or more, round up. If it is less than 5, keep the whole number the same.
3.47 has a 4 in the tenths place. Four is less than five, so 3.47 rounds down to 3.
Rounding to one decimal place works the same way, but you check one digit further: the hundredths digit. That is the second digit after the point.
When you estimate a sum, round each decimal to the nearest whole number first, then add. 4.83 rounds to 5, and 2.17 rounds to 2, so the estimate is 5 + 2 = 7.
Check the digit right after the place you are rounding to: 5 or more rounds up, below 5 stays the same.
Watch it
Where it sits
Learn first
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
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.