#### Answer

a. 3;
b. 3 or 6 depending if the trailing zeroes are significant or not;
c. 3;
d. 5;
e. 1 or 4 depending if the trailing zeroes are significant or not

#### Work Step by Step

a. There are 3 significant figures 3, 1, and 2. The zeroes preceding before are nonsignificant.
b. There are 3 significant figures 3, 1, and 2. The trailing zero after may or may not be significant. If the trailing zeroes are not significant, then there are 3 significant figures. If the trailing zeroes are significant, then there are 6 significant figures.
c. There are 3 significant figures 3, 1, and 2.
d. There are 5 significant figures 1, 3, 1, 2, and 7.
e. There is 1 significant figures, 2. The trailing zero after may or may not be significant. If the trailing zeroes are not significant, then there are 1 significant figures. If the trailing zeroes are significant, then there are 4 significant figures.