Question

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

• A. 5.65 $m^2$
• B. 56.5 $m^2$
• C. 565 $m^2$
• D. 5650 $m^2$

Answer 1

Answer: (B)

56.5 $m^2$

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