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ML Aggarwal Solutions Class 8 Mathematics Solutions for Mensuration Exercise 18.4 in Chapter 18 - Mensuration
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A cuboidal block of metal has dimensions 36 cm by 32 cm by 0·25 m. It is melted and recast into cubes with an edge of 4 cm.
(i) How many such cubes can be made?
(ii) What is the cost of silver coating the surfaces of the cubes at the rate of ₹0·75 per square centimeter?
(i) Given, Length of cuboid = 36 cm
Breadth of cuboid = 32 cm
Height of cuboid = 0·25 × 100 = 25 cm
So,
Volume of cuboid = lbh
= (36 × 32 × 25) cm3
= 28800 cm3
Volume of cube = (side)2
= (4)2
= 64 cm2
Hence, the number of cubes recasting from cuboid = 28800/64 = 450
(ii) Surface area of 1 cube = 6 × a2
= 6 × 16
= 96 cm2
So, the surface area of 450 cubes = 96 × 450
= 43200 cm2
Hence, the cost of silver coating on cubes = ₹0.75 × 43200
= ₹32400
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