Question

A cubical water tank holds 125 liters of water. What will the cost of whitewashing its outer walls be at a rate of $10 per square centimeter?

• A. $\$100000$
• B. $\$120000$
• C. $\$180000$
• D. $\$150000$

Answer 1

The correct option is A $\$100000$

The amount of water in the tank = volume of the tank

We know, 1 L $=1000$ cu cm
Therefore, $125L=125\times 1000=125000$ cu cm.
Thus, the volume of the tank $=s^3=125000$ cu cm , where s is the side of the tank.
$\Rightarrow s=\sqrt[3]{3125000}=50$ cm

Whitewashing will be done on the outer walls of the tank, which means the area that will be covered is the lateral surface area of the cuboidal tank.

Lateral surface area of the tank $=4\times s^2=4\times {50}^2=4\times 2500=10000$ sq cm

Cost of painting $=\$10$ per sq cm
Hence, the cost of whitewashing the tank $=10\times 10000=\$100000$.