Question

Radius and height of a cylinder are 7 cm and 14 cm respectively. It is divided along its axis vertically into equal parts. The increase in its total surface area is. (NTSE Stage - VRaj. (2008) (A) 392 sq. cm (B) 308 sq. cm (C) 196 sq. cm (D) 154 sq. cm​

Answer 1

Answer:

In volume of cylinder, the radius is multiplied by squaring it.

∴ Volume of cylinder B will be more than that of A

Volume of cylinder A

Radius(r)=

2

7

cm

Height(h)=14 cm

∴Volume of cylinder A=πr

2

h

=

7

22

×(

2

7

)

2

×14cc

=11×7×7=539cc

Volume of cylinder B

Radius(r)=

2

14

cm=7 cm

Height(h)=7 cm

∴Volume of cylinder B=πr

2

h

=

7

22

×(7)

2

×7cc

=22×7×7=1078cc

Thus, cylinder B has greater volume.

Now, Surface area of cylinder A=2πr(r+h)

=2×

7

22

×

2

7

(

2

7

+14)

=22×

2

35

=11×25=385 sq.cm

Now, Surface area of cylinder B=2πr(r+h)

=2×

7

22

×7(7+7)

=2×22×14=616 sq.cm

Thus, the cylinder of greater capacity has greater surface area.