How do I round a decimal to a requested place without changing the wrong digit?

First, translate the requested place into a position in the number. In 18.379, the first digit after the decimal point is the tenths digit, 3. The next is the hundredths digit, 7. The next is the thousandths digit, 9. Since the question asks for the nearest hundredth, 7 is your target. The target is the digit you may change; it is not necessarily the digit you inspect to decide what to do.

Now inspect exactly one place to the right of the target. Here that is the thousandths digit, 9. Because it is at least 5, increase the target 7 to 8, then remove the digits to the right. The result is 18.38. This is the rounding procedure described by OpenStax. [S1]

A useful note to write above your work is: “Target: hundredths, 7. Check: next digit, 9.” That makes the two roles visible and helps prevent checking the wrong place.

For this rounding rule, use only the digit immediately to the right of the target. Later digits do not change that decision. For example, assume the task is to round 6.249 to the nearest tenth. The tenths digit is 2; the digit immediately after it, in the hundredths place, is 4. Since 4 is less than 5, keep 2 and remove the digits to its right: the result is 6.2. The final 9 does not replace the 4 as the deciding digit. [S1]

Try marking the number before you calculate: underline the target digit, then circle just the next digit. If you find yourself comparing several digits, pause and re-identify the requested place. This example applies the stated rule; it is not a separate rule about reading every digit in the remaining tail.

Name the places from left to right after the decimal point before rounding: tenths, hundredths, thousandths. Then point to the place named in the question and count one position to the right for the deciding digit. For example, in 3.756, if the request is nearest hundredth, 5 is the target and 6 is the next digit. Raise 5 to 6 and remove the rest, giving 3.76. If the request were nearest tenth, the target would instead be 7 and the next digit would be 5. [S1]

A quick self-check is to say both positions aloud: “I’m rounding to the ___; the digit immediately to its right is ___.” If you can’t fill in those blanks confidently, don’t round yet—relabel the decimal places. This catches the common slip of using the target digit itself, or a digit farther to the right, as the deciding digit.

Use this copyable working format:

1. Asked place: [place]
2. Target digit: [digit]
3. Digit immediately to its right: [digit]
4. Decision: [raise target by 1 if this digit is 5 or greater; otherwise keep it]
5. Rounded result: [remove digits to the right]

Worked example: Round 42.683 to the nearest hundredth. Asked place: hundredths. Target digit: 8. Next digit: 3. Since 3 is less than 5, keep 8 and remove the digits to its right. Result: 42.68. The decision is based on the adjacent 3, not on the later digits. [S1]

This method addresses rounding to a requested decimal place using the procedure above. It does not establish how a particular worksheet, calculator, or other system handles special conventions beyond that procedure; if instructions specify a different convention, follow those instructions.