Step-by-step explanation:
We have to add two numbers and express the answer in scientific notation with the correct amount of significant figures (SF).
First we have to determine the number of SF that each number has after the decimal point.
7.30 x 10² = 2 SF in the decimal portion
2.80 x 10³ = 2 SF in the decimal portion
Now we can add these numbers in the normal way.
7.30 x 10² + 2.80 x 10³ = 3.530 x 10³
Finally the result can't have more significant figures to the right of the decimal than the least number of significant figures of any of the numbers that we are adding. So we have to round the decimal portion of the answer to the second figure.
7.30 x 10² + 2.80 x 10³ = 3.53 x 10³
Answer: 3.53 x 10³