Originally Posted by Val
The detailed answer was wrong because of significant figures: when multiplying, your answer can only have as many significant figures as the least accurate number you start with. So when the problem said "about 8" it was throwing out ONE significant figure. Ergo, the answer cannot include more than ONE significant figure.


Actually I missed the "about" before the "8." I only saw the second "about." (Ha! I fail the careful-reading test!) But I still think the significant digits analysis is too precise for the word "about." "About 8" could mean "somewhere between 7 and 9." Or it could mean "somewhere between 7.99 and 8.01." It all depends on your definition of "about." I still think the most correct answer is to do the exact calculation -- this is your least biased estimate of the real (unknown) value.