A golf ball has diameter equal to 4.1 cm. Its surface has 150 dimples each of radius 2 mm. Calculate totals area which is exposed to the surrounding assuming that the dimples are hemispherical.

Explanation

Area of normal ball=`4pi(4.1/2)^2`

`=16.81picm^2`

Area of 1 dimple=`2pir^2`

`=2*pi*(2/10)^2=2pi/25`

Area of 150 dimple=`150*2/25*pi=12picm^2`

Area of ball=`1681pi+12pi-6pi`

`=22.8picm^2`.