Question

Find the area to be painted for the given object. All dimensions including answer options are in cm.(Take $\pi =\frac{22}{7}$)

• A. 4070
• B. 4224
• C. 4884
• D. 4730

Answer 1

The correct option is B

4224

On close observation, we can see that the given object is made of 4 solids-

Cone on top
2 Frustums in the middle
Cylinder at the bottom

Area to be painted = CSA of cone + 2 CSA of frustums + CSA of cylinder + area of circular base

= $\pi$rl + 2.$\pi$(r +R)l + 2$\pi$rh + $\pi$$r^2$

= $\frac{22}{7}\times 7\times 25$ + 2.$\left(\frac{22}{7}\right)(7+14)\left(20\right)$ + $2\times \frac{22}{7}\times 7\times 20$ + $\frac{22}{7}\times 7\times 7$
= 550 + 2640 + 880 + 154

= 4224 $m^2$