Final answer:
To find the sum of the numbers, add them together and round the sum to three significant figures.
Step-by-step explanation:
To find the sum of the numbers, add them together:
11.24 + 3.4 + 1.000 = 15.64
To round the sum to the correct number of significant figures, we look at the number with the fewest significant figures, which is 1.000. Since there are three significant figures in this number, we round the sum to three significant figures:
15.64 rounded to three significant figures is 15.6.