This is the important question in the exam point of view because this question was ask in 2014 cbse board exam.

Question from RS Aggarwal

Chapter Mensuration

Volume and surface

Volume and Surface Area of Solid

Exercise 17A

Page number 786

Deepak BoraNewbie

# A 5-m-wide cloth is used to make a conical tent of base diameter 14 m and height 24 m. Find the cost of cloth used at the rate of 25 per meter.

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Let the slant height of the cone be ‘l’ meters.

height = 24 m

diameter = 14 m or radius = 7 m.

Then according to the question.

l² = h² + r²

l² = 24² + 7²

l² = 576 + 49

l² = 625

l = √625

l = 25 m

∴ the slant height of the cone is 25 m.

Curved Surface Area of the cone = πrl

= [22/7] × 7 × 25

Curved Surface Area of the cone = 550 m²

Now, length of the cloth used = Area/ width of the cloth

= 550/5

Length of the cloth used = 110 m

Cost of cloth = Rs. 25 per meter

Total cost of clothe used = 110 × 25

∴ Total cost of clothe used = Rs. 2750