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If Radii of Two Cylinders Are in the Ratio 4 : 3 and Their Heights Are in the Ratio 5 : 6, Find the Ratio of Their Curved Surfaces.

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Question

If radii of two cylinders are in the ratio 4 : 3 and their heights are in the ratio 5: 6, find the ratio of their curved surfaces.

Sum
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Solution

The ratio in radii of two cylinders = 4 : 3
and ratio in their heights = 5: 6

Let r1 and r2 be the radii and h1,h2 be their heights respectively.

∴ r1 : r2 = 4:3 and h1 : h2 = 5:6

∴ `r_1 = 4/3  "and"  (h_1)/(h_2) = 5/6`

∴ Surface area of the first cylinder = `2pir_1h_1`

and area of second cylinder = `2pir_2h_2`

`(2pir_1h_1)/(2pir_2h_2) = r_1/r_2 xx h_1/h_2 = 4/3 xx 5/6 = 20/18`

= `10/9 = 10 : 9`

∴ Ratio in their surface areas = 10 : 9

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Chapter 23: Surface Area, Volume and Capacity - Exercise 21 (D) [Page 243]

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Selina Concise Mathematics [English] Class 8 ICSE
Chapter 23 Surface Area, Volume and Capacity
Exercise 21 (D) | Q 10 | Page 243

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