NCERT Class 8 Mathematics Solutions: Chapter 11 –Mensuration Exercise 11.4 Part 4

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1. If each edge of a cube is doubled,

(i) How many times will its surface area increase?

(ii) How many times will its volume increase?

Consider the edge of cube be .

So, Surface area of the cube

When edge of cube is doubled, then

Surface area of the cube

So, the surface area will increase four times.

(ii) Volume of cube

When edge of cube is doubled, then

Volume of cube

So, the volume will increase times.

2. Water is pouring into a cuboidal reservoir at the rate of liters per minute. If the volume of reservoir is , find the number of hours it will take to fill the reservoir.

Given,

Volume of reservoir

Rate of pouring water into cuboidal reservoir

water filled in reservoir will take

water filled in reservoir will take hours

water filled in reservoir will take hours

It will take hours to fill the reservoir.