Answer
(a) 4 Significant Figures.
(b) 3 Significant Figures.
(c) 2 Significant Figures.
Work Step by Step
1. Identify and count the significant zeros:
(a) - All zeros between two nonzero digits are significant.
$1\underline 0 3.5 \space ^{\circ} F$
(b) - If there is a decimal point, all zeros to the right of the last nonzero digit are significant.
$1.2\underline 0 \times 10^{10}$
(c) - All zeros to the left of the first nonzero digit are not significant.
$0.46 \space s$
2. Add this number to the amount of nonzero digits:
(a) 3 + 1 = 4
(b) 2 + 1 = 3
(c) 2 + 0 = 2
