A new cylinder is formed from previous cylinder in which radius is increased by 12.5% and height is increased by 37.5%. What is the ratio of curved surface area of old cylinder to the curved surface area of new cylinder?
A new cylinder is formed from previous cylinder in which radius is increased by 12.5% and height is increased by 37.5%. What is the ratio of curved surface area of old cylinder to the curved surface area of new cylinder? Correct Answer 64 : 99
Given:
Percentage increase in radius = 12.5%
Percentage increase in height = 37.5%
Formula Used:
CSA of cylinder = 2πrh
where, r → Radius of base, h → Height of cylinder, CSA → Curved Surface Area of cylinder.
Calculations:
Let the old height and new height be h1 and h2 respectively.
Let the old radius and new radius be r1 and r2 respectively.
Percentage increase in radius = 12.5%
⇒ r2 = r1 × (1 + 12.5/100)
⇒ r2/r1 = 9/8 ----(1)
Percentage increase in height = 37.5%
⇒ h2 = h1 × (1 + 37.5/100)
⇒ h2/h1 = 11/8 ----(2)
Now, CSA of old cylinder/CSA of new cylinder = 2πr1h1/2πr2h2
⇒ CSA of old cylinder/CSA of new cylinder = (r1/r2) × (h1/h2)
From (1) and (2), we get
⇒ CSA of old cylinder/CSA of new cylinder = 8/9 × 8/11 = 64/99
⇒ CSA of old cylinder : CSA of new cylinder = 64 : 99
∴ The ratio of curved surface area of old cylinder to the curved surface area of new cylinder is 64 : 99.