RD Sharma 2020 solution class 9 chapter 19 Surface Area and Volume of a Right Circular Cylinder VSAQS

VSAQS

Page-19.31

Question 1:

Write the number of surfaces of a right circular cylinder.

Answer 1:

Let us list out the surfaces of a right circular cylinder.

1. Lateral surface

2. Lower circular base

3. Upper circular covering

Therefore, a right circular cylinder has a total of 3 surfaces.

Question 2:

Write the ratio of total surface area to the curved surface area of a cylinder of radius r and height h.

Answer 2:

Total Surface Area of a cylinder =

Curved Surface Area of a cylinder =

Ratio of Total Surface Area (TSA) to Curved Surface Area (CSA) is given by,

The ratio of Total Surface Area to Curved Surface Area is (h+r): h

Question 3:

The ratio between the radius of the base and height of a cylinder is 2 : 3. If its volume is 1617 cm3, find the total surface area of the cylinder.

Answer 3:

Given data is as follows

We have to find the total surface area of this cylinder

It is given that

Therefore

Therefore;

(As)

So;

Therefore;

Question 4:

If the radii of two cylinder are in the ratio 2 : 3 and their heights are in the ratio 5 : 3, then find the ratio of their volumes.

Answer 4:

Let r1 and r2 be the radii of the two cylinders respectively and h1 and h2 are the heights of the two cylinders respectively. It is given that and

We are asked to find the ratio of the volumes of the two cylinders

Now;

Therefore the ratio of the volumes of the two cylinders is

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