Answer:
30.24m
Explanation:
When adding numbers together, we round to the smallest number of decimal places of the numbers, which is 2 decimal places in this case.
24.686m + 2.343m + 3.21m = 30.239 m
≈ 30.24m (round to 2 d.p.)
When you round numbers to a certain digit (hundredth in this case), you would want to look on the digit on its right (thousandth in this case). If that digit is 1-4, you round the digit down. If that digit is 5-9, you round the digit up. Since the digit in the thousandths place is 9, you round the hundredth digit up from 3 to 4.
