RD Sharma - Mathematics

Book: RD Sharma - Mathematics

Chapter: 20. Surface Area and Volume of a Right Circular Cone

Subject: Mathematics - Class 9th

Q. No. 13 of Exercise 20.1

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There are two cones. The curved surface area of one is twice that of the other. The slant height of the later is twice that of the former. Find the ratio of their radii.

We have,

A1 = 2A2 = πr1l1= 2(πr2l2)

l2 = 2l1

r1l1=2r2×2l1 , = r1 = 4r2

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