ANSWER
2.48
EXPLANATION
We have to add like we normally do with whole numbers and put the decimal point in the same place it is in each summand:
The significant digits start with the first digit different from zero, reading from left to right:
This number has 4 significant digits in total: 2, 4, 7 and 9
Note that the numbers added don't have the same number of decimal places. The first one has three decimal places while the second one has two decimal places. This means that we have to round the answer to the second decimal place - which is hte 3rd significant digit. SInce the 4th significant digit is more than 5, we have to add one to the third significant digit:
[tex]2.479\Rightarrow2.48[/tex]