Question

Expressed in the correct number of significant figures the sum of 0.53 cm + 75.321 cm + 28.1 cm =

Answer 1

`\boxed{\text{104.0 cm}}`

Step-by-step explanation:

When adding or subtracting values, you must round your answer to the same "place" as the measurement with its last significant figure furthest to the left.

That is, you round off to the same number of decimal places as the measurement with the fewest decimal places.

`\begin{array}r0.5& \text{3 cm}\\+ 75.3& \text{21 cm}\\+ 28.1 & \quad\text{cm} \\= 103.9 &\text{51 cm}\\\end{array}`

The measurement of 28.1 cm has one digit after the decimal point, so you round the sum to have only one digit to the right of the decimal.

However, the number to be dropped (51) is greater than 5 with only zeros or nothing following the 5.

You must round up the answer. You increase the last significant digit by one.

`\text{The sum is $\boxed{\textbf{104.0 cm}}$}`