Now, Volume of the cylinder =
r
2
h
or 1.54 =
× 0.7 × 0.7 × h or, h =
= 1m
Hence, the height of the cylinder is 1 m.
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 liters that can be stored in the tank?
Answer:
49500 l
Solution:
Radius of the cylindrical tank (r) = 1.5 m (Given)
Length of the cylindrical tank (l) = 7 m (Given)
Volume of the tank =
× 1.5 × 1.5 × 7m3
= 49.50 m
3
= 49.50 × 100 × 100 × 100 cm
3
= 49500000 cm
3
=
liters = 49500 liters [
1000 cm
3
= 1 liters.]
Hence, the volume of the milk that can be stored in the tank is 49500 liters.
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:
(i) 4 times (ii) 8 times
Solution:
Let each edge of the cube be x
Surface area of the cube = 6x
2
, Volume of the cube = x
3
When each edge of the cube is 2x, then,
the surface area of the new cube = 6 (side)
2
= 6 (2x)
2
= 6 × 4x
2
= 24x
2