Question

17. If a diameter of a sphere is increased by 20%, then its radius increases by
(a) 5%
(b) 10%
(C) 20%
(d) 40%
​

Answer 1

Step-by-step explanation:

Let the radius of original circle =r

∴ Area of original circle =πr

2

But, the radius of the circle is increased by 20%

∴ Radius of new circle R=

100

20r

+r=1.2r

Area of new circle =πR

2

=π(1.2r)

2

=1.44πr

2

Increased area =1.44πr

2

−πr

2

=0.44πr

2

Percentage increase in area =

πr

2

0.44πr

2

×100=44%

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Answer 2

Step-by-step explanation:

d = 2r which means d is directly proportional to r.

So, they will change in the same amount.

So, the radius will also get increased by 20%

Otherwise, see the photo.