Question

The radii of two right circular cylinders are in the

ratio 3 : 4 and their heights are in the ratio 1 : 2.

Calculate the ratio of their curved surface areas​

Answer 1

Answer: 5:6

Step-by-step explanation: Let the radii of 2 cylinders be 2r and 3r respectively and their heights be 5h and 4h respectively.

Let S  

1

​  

 and S  

2

​  

 be the curved surface areas of two cylinders.

S  

1

​  

→ CSA of cylinder of radius 2r and height 5h=S  

1

​  

=2×π×2r×5h=20πrh

S  

2

​  

→ CSA of cylinder with radius 3r and height 4h=S  

2

​  

=2×π×3r×4h=24πrh

∴  

S  

2

​  

 

S  

1

​  

 

​  

=  

24πrh

20πrh

​  

=  

6

5

​  

 

∴S  

1

​  

:S  

2

​  

=5:6.