Find the surface area of a sphere of diameter 3.5 m.

Given,

Diameter of sphere (d) = 3.5 m

Radius of sphere (r) = $\dfrac{\text{Diameter}}{2} = \dfrac{3.5}{2}$ = 1.75 m

By formula,

Surface area of a sphere (A) = 4πr²

Substituting values we get :

$A = 4 \times \dfrac{22}{7} \times (1.75)^2 \\[1em] = 4 \times \dfrac{22}{7} \times 1.75 \times 1.75 \\[1em] = 4 \times 22 \times 0.25 \times 1.75 \\[1em] = 38.5 \text{ m}^2.$

Hence, the surface area of a sphere = 38.5 m².