 # RD Sharma Solutions Class 8 Mathematics Solutions for Volume Surface Area Cuboid Cube Exercise 21.4 in Chapter 21 - Volume Surface Area Cuboid Cube

Question 7 Volume Surface Area Cuboid Cube Exercise 21.4

A closediron tank 12 m long, 9 m wide and 4 m deep is to be made. Determinethe cost of iron sheet used at the rate of Rs. 5 per metre sheet, sheet being 2 m wide.

Given,

Length of tank, l = 12 m Width of tank, b = 9m

Depth of tank, h = 4m

Area of sheet required = total surface area of tank

= 2 (lb×bh×hl)

= 2 (12×9 + 9×4 + 4×12)

= 2 (108 + 36 + 48)

= 2 (192)

= 384 m2

Let length be l1

Breadth be b1 Given, b1 = 2m l1 × b1 = 384

l1 = 384/b1

= 384/2

= 192m

∴ Cost of iron sheet at the rate of Rs 5 per metre = 5 × 192 = Rs 960

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