a girl wishes to prepare birthday caps in the form of right circular cones for her birthday party, using a sheet of paper whose area is 5720cm²,how many caps can be made with radius 5cm and height 12cm.
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mark as brainlist .Example 1 :
A right angled triangle PQR where angle Q = 90 degree is rotated about QR and PQ. If QR = 16 cm and PR = 20 cm, compare the curved surface areas of the right circular cones so formed by the triangle.
Solution :
radius of cone = 16 cm
Slant height = 20 cm
If the triangle is rotated about PQ :
Curved surface area = Πrl
= Π ⋅ 16 ⋅ 20
= 320Π cm2
height = √(l2 - r2)
= √(202 - 162)
= √144
h = 12
If the triangle is revolved about QR, then radius will be 12 cm
Curved surface area = Πrl
= Π ⋅ 12 ⋅ 20
= 240Π cm2
So, curved surface area of cone is larger when it is revolved about PQ.
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