Question

The diameters of two cones are equal. If their slant heights are 7:4, find the ratio of their curved surface areas.

Answer with complete calculations.

Points : 15 ☺

Answer 1

as the diameter of two cones are equal then ,
their radius will also be equal.
let the CSA of the cones be  πrl1 and πrl2 
the ratio of their CSA is nothing but,
=CSA of 1st cone/CSA of 2nd cone
=  πrl1/  πrl2
as pi and radius are common to both they are cancelled.=  l1 / l2
we know that   l1 / l2=7/4 
so the ratio of their CSA is also same=7/4
hope it helps!!!!

Answer 2

Hope this helps you...
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The diameter of two cones are equal , therefore their radius is also equal.
let the CSA of the cones be πrl1 and πrl2
.:.
=CSA of 1st cone/CSA of 2nd cone
= πrl1/ πrl2 = l1 / l2 and as l1 / l2=7/4
.:. the ratio of their CSA is also same=7/4