7.55 + 17.002 = ?
First, we have to determine the number of significant figures that each number has.
7.55: 3 SF and 2 SF after the decimal point.
17.002: 5 SF and 3 SF after the decial point.
Second, perform the mathematical operation as we usually do.
7.55 + 17.002 = 24.552
Finally we determine the correct number of SF. When adding or substracting the rule says: "The final answer may have no more SF after the decimal point than the least number of significant figures in the operation". Since 7.55 has 2 SF after the decimal point, we must round the result of the addition to the second place to the right of the decimal point.
Rounding 24.552 we get 24.55.
Answer: 24.55
