NCERT Solutions for Class 8 Maths Chapter 11 Mensuration Ex 11.4
NCERT Solutions for Class 8 Maths Chapter 11 Mensuration Ex 11.4
These NCERT Solutions for Class 8 Maths Chapter 11 Mensuration Ex 11.4 Questions and Answers are prepared by our highly skilled subject experts.
NCERT Solutions for Class 8 Maths Chapter 11 Mensuration Exercise 11.4
Question 1.
Given a cylindrical tank, in which situation will you find surface area and in which situation volume.
(a) To find how much it can hold.
(b) Number of cement bags required to plaster it.
(c) To find the number of smaller tanks that can be filled with water from it.
Answer:
(a) Volume
(b) Surface area
(c) volume
Question 2.
Diameter of cylinder A is 7 cm, and the height is 14 cm. Diameter of cylinder B is 14 cm and height is 7 cm. Without doing any calculations can you suggest whose volume is greater? Verify it by finding the volume of both the cylinders. Check whether the cylinder with greater volume also has greater surface area?
Answer:
Volume of cylinder B will be greater than the volume of cylinder A.
For cylinder A
= 
Thus, cylinder B has greater volume than cylinder A.
Thus, the cylinder of great capacity has greater surface area.
Question 3.
Find the height of a cuboid whose base area is 180 cm2 and volume is 900 cm3?
Answer:
Base area of the cuboid = 180 cm2
∴ lb = 180
Volume of the cuboid = 900 cm3
Base Area × height = 900
lb × h = 900
180 × h = 900
h= 900/180 = 5
∴ Height of the cuboid = 5 cm
Question 4.
A cuboid is of dimensions 60 cm × 54 cm × 30 cm. How many small cubes with side 6 cm can be placed in the given cuboid?
Answer:
Here l = 60 cm, b = 54 cm, h = 30 cm
Volume of the cuboid = l × b × h cm3 = 60 × 54 × 30 cm3
Side of a cube = 6 cm
Volume of cube = l3 cm3 = 6 × 6 × 6 cm3
Question 5.
Find the height of the cylinder whose volume is 1.54 m3 and diameter of the base is 140 cm?
Answer:
Question 6.
A milk tank is in the form of cylinder whose radius is 1.5 m and length is 7 m. Find the quantity of milk in litres that can be stored in the tank?
Question 7.
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?
Answer:
Let the original edge be ‘x’
∴ increased edge 2x
∴ original surface area = 6x2
increased surface area = 6(2x)2 = 24x2
Question 8.
Water is pouring into a cuboidal reservoir at the rate of 60 litres per minute. If the volume of reservoir is 108 m3. Find the number of hours it will take to fill the reservoir.
Answer:
Volume of the reservoir = 108 m3
= 108 × 1000 litres = 108000 litres
Amount of water poured in one minute = 60 litres
Time taken to fill the reservoir = 108000/60
= 1800 minutes 1800/60 hours = 30 hours
The required number of hours = 30.
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