What are the steps you would follow to round 439 to the nearest ten?

Answer 1

1. None of the digits before the tens' digit (4) should change.

2. Identify the digit in the tens' place (3).

3. Identify the digit in the units' place.

4a. If it is 0, leave the tens' digit unchanged

4b. If it is 1, 2, 3 or 4 then the number needs to be rounded down. So replace the units digit by 0.

4c. If it is 6, 7, 8 or 9 then the number needs to be rounded up. So increase the tens' digit by 1 (from 3 to 4), and replace the units digit by 0.

4d. If it is 5 then, in order to avoid introducing bias, you need to round up half the time and round down half the time. The way to do this is to make the tens' digit even: if it is already even then do nothing, if it is odd then add 1. And replace the units' digit by 0.

In this case the answer is 440.

Two things to bear in mind:

Many schools opt for the naive approach of applying rule 4b (instead of 4d) for the digit 5.

In the case of rule 1, you need to bear in mind any carry over from rounding up the tens.