Question 5: What length of tarpaulin 3 m wide will be required to make conical tent of height 8 m and base radius 6 m? Assume that the extra length of material that will be required for stitching margins and wastage in cutting is approximately 20 cm (Use π = 3.14).

**Answer:** h = 8 m, r = 6 m

Here; `l^2 = h^2 + r^2`

`= 8^2 + 6^2`

`= 64 + 36 = 100`

Or, `l = 10 m`

CSA of cone `= π rl`

`= 3.14 xx 6 xx 10 = 188.4 sq m`

Hence, required length of material `= (188.4/3) + 0.2 m`

`= 62.8 + 0.2 = 63 m`

Question 6: The slant height and base diameter of a conical tomb are 25 m and 14 m respectively. Find the cost of white-washing its curved surface at the rate of Rs 210 per 100 m^{2}.

**Answer:** l = 25 m, d = 14 m or, r = 7 m

CSA of cone `= π rl`

`= (22/7) xx 7 xx 25 = 550 sq m`

`Co\st = Ar\ea\xx\ra\te`

`= 550 xx (210/100) = Rs. 1155`

Question 7: A joker’s cap is in the form of a right circular cone of base radius 7 cm and height 24 cm. Find the area of the sheet required to make 10 such caps.

**Answer:** r = 7 cm, h = 2 cm

Here; `l^2 = h^2 + r^2`

`= 24^2 + 7^2`

`= 576 + 49 = 625`

Or, `l = 25 cm`

CSA `= π rl`

`= (22/7) xx 7 xx 25 = 550 sq cm`

Area of sheet for 10 caps `= 550 xx 10 = 5500 sq cm`

Question 8: A bus stop is barricaded from the remaining part of the road, by using 50 hollow cones made of recycled cardboard. Each cone has a base diameter of 40 cm and height 1 m. If the outer side of each of the cones is to be painted and the cost of painting is Rs 12 per m^{2}, what will be the cost of painting all these cones? (Use π = 3.14 and take ∠1.04 = 1.02)

**Answer:** d = 40 cm or, r = 20 cm, h = 1 m

Here; `l^2 = h^2 + r^2`

`= 1^2 + (0.2)^2`

`= 1 + 0.04 = 1.04`

Or, `l = sqrt1.04 = 1.02`

CSA of cone `= π rl`

`= 3.14 xx 1.02 xx 0.2`

CSA of 50 cones `= 3.14 xx 1.02 xx 0.2 xx 50`

`= 3.14 xx 1.02 xx 10 = 32.028`

`Co\st = Ar\ea\ xx Ra\te`

`= 32.028 xx 12 = Rs. 384.33`

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