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2022.01.21 15:35, Hold the with your on of the and rotate the triangle, SURFACE AREAS AND VOLUMES, 4., in m2., the curved surface of the pillar at the rate of 12.50 per m?., cylinder is 0.7 m, find its height., The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find, (1) its inner curved surface area,, (ii) the cost of plastering this curved surface at the rate of 40 per m, In a hot water heating system, there is a cylindrical pipe of length 28 m and diameter, 5 cm. Find the total radiating surface in the system., Find, he lateral or curved surface area of a closed cylindrical petrol storage tank that is, 4.2 m in diameter and 4.5 m high., 1., of the steel actually used was wasted in, 12, (i) how much steel was actually used, if, making the tank., 10. In Fig. 13.12, you see the frame of a lampshade. 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., 11. The students of a Vidyalaya were asked to participate in a competition for making and, n decorating penholders in the shape of a cylinder with a base, using cardboard. Each, penholder was to be of radius 3 cm and height 10.5 cm. The Vidyalaya was to supply, the competitors with cardboard. If there were 35 competitors, how much cardbuard, was required to be bought for the competition?, So far, we have been generating solids by stacking up congruent figures. Incidentally,, such figures are called prisms. Now let us look at another kind of solid which is not a, prism (These kinds of solids are called pyramids.). Let us see how we can generate, them., 13.4 Surface Area of a Right Circular Cone, Activity : Cut out a right-angled triangle ABC right angled at B. Paste a long thick, iing along one of the perpendicular sides say AB of the triangle [see Fig. 13.13(a).