Question

20. The difference between the outer curved
surface area and the inner curved surface area
of a hollow cylinder is 352 cm? If its height
is 28 cm and the volume of material in it is
704 cm; find its external curved surface area,
​

Answer 1

Answer:

HI MATE !

Let r

1

= outer surface area, r

2

= inner surface area, length h=28

Outer curved surface area of cylinder =2πr

1

hcm

2

Inner curved surface area of cylinder =2πr

2

hcm

2

Difference between two curved surface area cylinder =2π(28)(r

1

−r

2

)=352cm

2

r

1

−r

2

=2.......(1)

Volume of cylinder =π(r

1

2

−r

2

2

)h=π(r

1

2

−r

2

2

)(28)=704

r

1

2

−r

2

2

=8.....(2)

Solving, (2),(r

1

−r

2

)(r

1

+r

2

)=8

2(r

1

+r

2

)=8

r

1

+r

2

=4.....(3)

From (1) and (3), r

1

=3,r

2

=1

External curved surface =2πrh=2π(3)(28)=528cm 2

You can also refer to the above pic.

Hope my answer helps you.... ✌️

☺️

Answer 2

Not sure abt what the answer is