We have
Diametre of golf ball= 4.1cm
radius of each dimplets= 2mm
surface area of the ball =4Ï€r
2
=4π×(
2
4.1
​
)
2
cm
2
=16.81cm
2
In case of each dimplets, surface area equal to πr
2
(r is the radius of each dimple) is removed from the surface of the ball where as the surface area of hemisphere i.e 2Ï€r
2
is exposed to the surroundings
Total surface area exposed to the surroundings = surface area of the ball
−150πr
2
+150×2πr
2
=16.81Ï€+150Ï€r
2
=
⎩
⎪
⎨
⎪
⎧
​
16.81π+150π×(
10
2
​
)
2
âŽ
⎪
⎬
⎪
⎫
​
cm
2
=22.81×
7
22
​
cm
2
=71.68cm
2
