Chapter 13 : Surface areas and volumes

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(i) determine the area of the sheet

(ii) the cost of sheet for it, if a sheet measuring 1 m2 costs Rs.20.

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The floor of a rectangular hall has a perimeter 250 m. If the cost of painting the four walls at the rate of Rs 10 per m2 is 15000, find the height of the hall (in meters).

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A small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is 30cm long, 25cm wide and 25cm high.

(i) What is the area of the glass?

(ii) How much of tape is needed for all the 12 edges?

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(i) its inner curved surface area

(ii) the cost of plastering the curved surface at the rate of Rs. 40 per m2

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(i) The lateral or curved surface area of a closed cylindrical petrol storage tank that is 4.2 m in diameter and 4.5 m high.

(ii) How much steel was actually used, if 112 of the steel actually used was wasted in making the tank?

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It is required to make a closed circular cylindrical tank of height 1 m and base diameter 140 cm from a metal sheet. How many square meters of the sheet is required for the same?

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In the figure, you see the frame of a lampside. It is to be covered with a decorative cloth. The frame has a base diameter of 20 cm and height of 30 cm. A margin of 2.5 cm is to be given for folding it over the top and bottom of the frame. Find how much cloth is required for covering the lampshade.

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A metal pipe is 77 cm long. The inner diameter of a cross section is 4 cm, the outer diameter being 4.4 cm (see figure). Find its

(i) Inner curved surface area.

(ii) Outer curved surface area

(iii) Total surface area

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