Question

A big iron boiler tank has a cylindrical structure which is open from the top. Its height is 10 m and radius is 7 m. It gets painted at a rate of 3 m${}^2$ per day. Then find the number of days in which the tank gets painted completely? (Take $\pi =\frac{22}{7}$)

• A. 192
• B. 202
• C. 198
• D. 208

Answer 1

The correct option is C

198

Given, radius of the boiler = 7 m
Height of the boiler = 10 m

Since the iron boiler tank is opened on top,
Total surface area of the boiler = Curved surface area + Base area
$=2\pi rh+\pi r^2$
$=2\times \frac{22}{7}\times 7\times 10+\frac{22}{7}\times 7^2$
$=440+154$
$=594m^2$

$\therefore$ Total number of days in which the tank gets painted completely
$=\frac{\text{Total Surface area of tank}}{\text{Area painted per day}}$
$=\frac{594m^2}{3m^2/day}=198$ days