Question

19. The sum of the inner and the outer curved
surfaces of a hollow metallic cylinder is
1056 cm2 and the volume of material in it is 1056
cm. Find its internal and external radii. Given
that the height of the cylinder is 21 cm.​

Answer 1

Answer:

HI MATE !

Let us take external radii =R

Inner radii=r and height =21 cm

As sum of the inner and the outer curved surfaces of a hollow metallic cylinder is 1056 cm2,

πRh+πrh=1056

R+r=8 ---eq 1

and volume of material =1056 cm

3

πR

2

h−πr

2

h=1056

R

2

−r

2

=16

(R+r)(R−r)=16

R−r=2 ----eq2

After adding eq1 and eq2 we get,

2R=10

R=5

r=3

external radius R is 5 cm and internal radius r is 3 cm.

Thus the sum of the external and internal radii is 5 + 3 = 8 cm

You can refer to the above pic also.

Hope my answer helps you.... ✌️

☺️