math/chem significant figures
posted by kelie on .
Which of the answers for the following conversions contains the correct number of significant figures?
A)2.543 m x 39.4in/1m=100.1924in
B)2 L x 1.06qt/1L=2.12 qt
C)24.95 min x 1hr/60 min=0.4158 hr
D)12.0 ft x 12in/1ft x 2.54cm/1in=370cm
E)24.0 kg x 1lb/2.20kg=11lb
the answer is c but i don't understand why. i thought you round the answer based on the number of sig figs of the lowest measurement so why wouldn't D be the answer?

C is correct
D is correct if the zero has a line over it (ie, a significant zero)
c is correct becaues 1hr/60 min is NOT a measurement, it is a fundamental conversion. 1hr/60min is an infinite number of significant digits.
d is correct only if the last zero is designated as significant, we once put a line over the zero to indicated it is significant. It doesn't show that here. 
but i though d would be rounded to 2 sf, not 3 because of the 12 in. or is that wrong because 12in/ft is not a measured number?