Surface area of a solid sphere of radius 5 cm is equal to the difference of outer and inner surface

M4maths Previous Puzzles

13 Mar 2013 sphere

Surface area of a solid sphere of radius 5 cm is equal to the difference of outer and inner surface area of a hollow sphere of thickness 1 cm, Product of the inner and outer radius will be

OPtion

1) 156
2) 1
3) 78
4) 72
5) 1.6
6) .9
7) 60
8) 65
9) 100
10) None of these

Solution

By the given condition
4(pi)*5^2 = 4(pi)*r^2 - 4(pi)*(r-1)^2 (let the radius of hollow sphere be r)
By solving equation
find r and (r-1)
r*(r-1) = 12*13 = 156

Correct Option: 1 Best Solution (0)