# ML Aggarwal Solutions Class 8 Mathematics Solutions for Mensuration Exercise 18.4 in Chapter 18 - Mensuration

Question 11 Mensuration Exercise 18.4

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)

= (4)2

= 64 cm2

Hence, the number of cubes recasting from cuboid = 28800/64 = 450

(ii) Surface area of 1 cube = 6 × a

= 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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