# Ex.11.4 Q8 Mensuration Solution - NCERT Maths Class 8

## Question

Water is pouring into a cuboidal reservoir at the rate of \(60\) liters per minute. If the volume of reservoir is \(108{\rm{ }}{{\rm\,{m}}^3}\), find the number of hours it will take to fill the reservoir.

## Text Solution

**What is Known?**

Shape of the reservoir is cuboidal. The rate of pouring water into reservoir is given.

**What is unknown?**

(i) Increased surface area and volume of a cube.

(ii)How much time it will take to fill the reservoir?

**Steps:**

Volume of the reservoir

\[\begin{align} &= 108\rm {m^3}\\ &= 108 \times 1000\,\,{\rm{litres}}\\&= {\rm{ 108000}}\,\,{\rm{litres}}\end{align}\]

Volume of water flowing into the reservoir in \(1 \) minute \(=\) \(60\rm\,L.\)

In 1 hour

\[\begin{align}&=(60 \times 60)\,\,{\text{Litres per hour}}\\&=3600\,\,{\rm{litres}}/{\rm{hour}}\end{align}\]

Required number of hours

\[\begin{align} &=\frac{108000}{3600}\,\,\text{hours} \\ &=30\,\,\text{hours}\end{align}\]

Thus , it will take \(30\) hours to fill the reservoir.