Why is the final answer for the micrometer measurement 3% instead of 2.9%?

[trew]

Homework Statement

as below

Relevant Equations

as below

I thought that since he micrometer is to 2 significant figures (0.35 and 0.01mm) that the final answer should also be to 2 sig.figs, thus answer A.

But the final answer is C, 3%. Can someone explain why?

 

[Orodruin]

0.01 is one significant digit. Leading zeros do not count.

 

[haruspex]

0.01 is one significant digit.

Yes, but the marks on the micrometer will be rather more accurate than to the nearest 0.01mm. If you take a reading to the nearest 0.01mm according to the gradations, the actual error will be +/-(0.005+ε) where ε is the error range for the gradations.
So there is insufficient information to say how many significant digits should be quoted, but two seems reasonable.

Worse, 0.005/0.35 = 1.4%, not 2.9%.