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Question
A closed box is cuboid in shape with length = 40 cm, breadth = 30 cm and height = 50 cm. It is made of a thin metal sheet. Find the cost of metal sheet required to make 20 such boxes, if 1 m2 of metal sheet costs Rs. 45.
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Solution
Length of closed box (l) = 40 cm
Breadth (b) = 30 cm
and height (h) = 50 cm
Total surface area = 2 (lb + bh + hl)
= 2 (40 × 30 + 30 × 50 + 50 × 40) cm2
= 2 (1200 + 1500 + 2000) cm2
= 2 × 4700
= 9400 cm2
Surface area of sheet used for 20 such boxes = 9400 × 20 = 188000 cm2
∴ 188000 cm2 = `(188000)/(100 xx 100) = 18.8 " m"^2`
Cost of 1 m2 sheet = Rs. 45
Total cost = ₹ 18.8 × 45 = ₹ 846
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