Rounding to a required degree of accuracy
Round decimals to any place using place-value understanding; round any whole number to a required degree of accuracy
What a learner can do afterwards
- Round 3.4567 to 2 decimal places (3.46)
- Round 7,654,321 to the nearest 100,000 (7,700,000)
- Use rounding to estimate 4.83 × 2.17 ≈ 5 × 2 = 10
1 · Read
A decimal number has place-value columns after the point too: tenths, then hundredths, then thousandths. To round a decimal, first decide which place you want to keep. Then look at the very next digit to its right.
Round 3.4567 to 2 decimal places. Keep the tenths and hundredths digits: 3.45. Look at the next digit, which is 6. Since 6 is 5 or more, the hundredths digit rounds up by one, giving 3.46.
The same rule works for big whole numbers. To round 7,654,321 to the nearest 100,000, keep the digit in the hundred-thousands place (6) and look at the digit right after it (5). Since 5 is 5 or more, that digit rounds up, giving 7,700,000.
Rounding also gives quick estimates. To estimate 4.83 × 2.17, round each number to the nearest whole number first. 4.83 rounds to 5 and 2.17 rounds to 2. Then multiply the easy numbers: 5 × 2 = 10. The real answer should land near 10.
Rounding any number means keeping the place you want and checking only the very next digit to decide whether it goes up.
2 · Watch
Take it off screen
Where it sits
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.