Final answer:
When summing numbers like 15.3 and 1.285, the answer must be rounded to one decimal place, yielding 16.6. For sums like 1.005 + 17.88, the total should be rounded to four significant figures, which is 18.89.
Step-by-step explanation:
Calculating with Significant Figures
When adding the numbers 15.3 and 1.285, the sum is 16.585. However, we must express the answer with the correct number of significant figures. Since 15.3 has the least number of significant digits after the decimal point (one digit), the sum must be rounded to the tenths place. Therefore, 16.585 is rounded to 16.6.
For another example, calculating the sum 1.005 and 17.88, the calculator gives 18.885. To maintain the proper number of significant figures (four, since 1.005 has the least), the sum is rounded to 18.89.
In situations where the problem includes weight measurements such as 13.5 pounds and 10.2 pounds, the total weight would be calculated as 23.7 pounds because each number has three significant figures, and the least accurate number (10.2) has one digit after the decimal.