Ex.11.4 Q8 Mensuration Solution - NCERT Maths Class 8

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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?


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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