Significant figures with multiplication and addition?

Question

I have this problem for my chem hw, I can't seem to get right...

Calculate with the correct number of significant figures.

(7.87g) / (16.1g - 8.14g) = ?

The answer is not 0.989, 1.00, 1., 0.984, or 0.996. But if it is one of those, than something's wrong with the system, because my homework is online.

According to my textbook, with multiplication problems, "the answer contains the same number of significant figures as in the measurement with the fewest significant figures."

For addition problems, "the answer has the same number of decimal places as there are in the measurement with the fewest decimal places."

Help?

Answer 1

I'll do nothing except follow the standard order of operations and the two instructions you quoted.  Because of the parentheses, I need to perform the subtraction first.

( 7.87g ) / ( 16.1g - 8.14g )

For addition problems, the answer has the same number of decimal places as there are in the measurement with the fewest decimal places.

The subtraction is 1 and 2 decimal places, so the result is 1 decimal place.

( 7.87g ) / ( 16.1g - 8.14 )

( 7.87g ) / ( 8.0 )

For multiplication problems, the answer contains the same number of significant figures as in the measurement with the fewest significant figures.

The division has 3 and 2 significant digits, so the result has 2 significant digits.

7.87g  /  8.0g

0.98g

You may want to check my math, and check my counting of digits.