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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. - CBSE Class 9 - Mathematics

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Question

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.  

Solution

Let curved surface area off 1^st cone = 2x 

CSA of 2^nd cone=x 

`"and slant height of 1 ^st cone=h "`

`"and slant height of 2 ^nd cone = 2h"` 

`"CSA of 1^st cone" / "CSA of 2^nd cone"=(2x)/x=2/1` 

⇒ `(pir_1l_1)/(pir_2l_2)=2/1` 

⇒ `r_1h/r_2h=2/1⇒r_1/r_2=4/1` 

 

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APPEARS IN

 RD Sharma Solution for Mathematics for Class 9 by R D Sharma (2018-19 Session) (2018 to Current)
Chapter 20: Surface Areas and Volume of A Right Circular Cone
Ex.20.10 | Q: 13 | Page no. 8
Solution 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. Concept: Surface Area of a Right Circular Cone.
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