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

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## 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.

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