# NCERT Class 8 Mathematics Solutions: Chapter 11 – Mensuration Exercise 11.4 Part 1

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1. Given a cylindrical tank, in which situation will you find surface are 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:

We find area when a region covered by a boundary, such as outer and inner surface area of a cylinder, a cone, a sphere and surface of wall or floor.

When the amount of space occupied by an object such as water, milk, coffee, tea, etc., then we have to find out volume of the object.

(a) Volume

(b) Surface area

(c) Volume

2. Diameter of cylinder and the height is . Diameter of cylinder and height is . 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:

Yes, we can say that volume of cylinder is greater, since radius of cylinder is greater than that of cylinder (and square of radius gives more value than previous).

Diameter of cylinder

Radius of cylinder

And height of cylinder

Volume of cylinder

Now,

Diameter of cylinder

Radius of cylinder

And,

Height of cylinder

Volume of cylinder

Total surface area of cylinder

Total surface area of cylinder

Yes, cylinder with greater volume also has greater surface area.