Answer
$21.3$ or $2.13\times10^{1}$
Work Step by Step
The least precisely known quantity, $0.000456$, has three significant figures. As this is a case of division or multiplication, the final result must also contain only three significant figures.
We perform the calculation $\frac{62.356}{0.000456\times6.422\times10^{3}}$ by using an electronic calculator.
The result displayed on the calculator is 21.29331
Rounding off to three significant figures, the result is properly expressed as
$21.3$ or $2.13\times10^{1}$
