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. If that digit is 5 or more, the kept digit goes up by one. If it is less than 5, the kept digit stays the same. Then drop the digits after the kept place.
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, the 6 goes up to 7. In a whole number, the places after the kept digit become zeros instead of being dropped, 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.
All practice questions and the reading are original to this dataset. The videos are Khan Academy videos; their terms are not recorded.
2 · Watch
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