Question

A big iron boiler tank which is cylindrical in shape is open at the top. Its height is 10 $\text{m}$ and radius is 7 $\text{m}$. It gets corroded at a rate of 3 ${\text{m}}^2$/day. The number of days it will take to corrode completely is ____ .
$(use\pi =\frac{22}{7})$

• A. 192
• B. 202
• C. 198
• D. 208

Answer 1

The correct option is C

198

Surface area of the boiler = Curved surface area of boiler + Base area of boiler
$=2\pi rh+\pi r^2$
$=2\times \frac{22}{7}\times 7\times 10+\frac{22}{7}\times 7^2$
$=440+154$
$=594m^2$

Now, number of days to corrode
$=\frac{TotalSurfaceAreaoftank}{Areacorrodedperday}$
$=\frac{594}{3}$
$=198days$

$\therefore$ Boiler will take 198 days to get corroded completely.