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Question 3, , The floor of a rectangular hall has a perimeter 250 m. If the cost of painting the four walls at, the rate of 210 per m* is 215000, find the height of the hall, [Hint : Area of the four walls = Lateral surface area.], , Answer 3, , Perimeter of rectangular hall = 2(I + b) = 250 m, Total cost of painting = 715000, Rate per m?=210, , ‘Area of four walls = 2(I + b) hm, Al,, , (250xh)«10 = %15000, , = 2500xh = 215000, , = h = 15000/2500 m, =>h=6m, , Thus the height of the hall is 6 m., , , , (250xh) m?, , , , , , , , , Question 4, , The paint in a certain container is sufficient to paint an area equal to 9.375 m*, How many, bricks of dimensions 22.5 omx10 cmx7.5 cm can be painted out of this container?, , Answer 4, , Volume of paint = 9.375 m? = 93750 cm?, , Dimension of brick = 22.5 cmx10 omx7.5 om, , Total surface area of a brick = 2(Ib + bh + Ih) cm?, , = 2(22.5*10 + 107.5 + 22.5%7.5) cm?, , = 2(225 + 75 + 168.75) cm?, , = 2468.75 cm? = 937.5 cm*, , Number of bricks can be painted = 93750/937.5 = 100, , Question 5, , A cubical box has each edge 10 cm and another cuboidal box is 12.5 om long, 10 om wide, and 8 om high., , (i) Which box has the greater lateral surface area and by how much?, , (ii) Which box has the smaller total surface area and by how much?, , Answer 5, , (i) Lateral surface area of cubical box of edge 10cm = 4x10? cm? = 400 cm?, , Lateral surface area of cuboid box = 2(I+b)xh, , = 2x(12.5+10)x8 cm?, , = 222.5%8 cm? = 360 cm?, , Thus, lateral surface area of the cubical box is greater by (400 — 360) cm? = 40 cm?, (ii) Total surface area of cubical box of edge 10 cm =6x102cm2=600em2, , Total surface area of cuboidal box = 2(Ib + bh + Ih), , = 2(12.5*10 + 10x8 + 8x12.5)cm?, , = 2(125+80+100) cm?