Physics

The diameter of a sphere is $$4.24\ m$$. Its surface area with due regard to significant figures is :


ANSWER

56.5 $${ m }^{ 2 }$$


SOLUTION
$$d=4.24\;m$$
$$SA=$$ Surface area $$=4\pi r^{2}=4\pi \left ( \dfrac{d}{2} \right )^{2}=\pi d^{2}$$
$$=\pi \left ( 4.24 \right )^{2}$$
$$=56.47\ m^{2}$$
Since significant figure in 4.24 is 3, so we express the answer in 3 significant figures.
$$SA=56.47\ m^2 \approx 56.5\ m^2$$
(Rounding off to 3 significant figures - if digit to be dropped is more than 5, the preceding digit is raised by 1)
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