21.  The areas of the three adjacent faces of a rectangular box which meet in a point are known. The product of these areas is equal to :


the volume of the box
twice the volume of the box
the square of the volume of the box
the cube root of the volume of the box


Answer

 Option

Let length = l, breadth = b and height = h, Then, Product of areas of 3 adjacent faces = (lb * bh * lh) = (lbh)2 = (Volume)2.

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22.  The capacity of a tank of dimensions (8 m * 6 m * 2.5 m) is


120 litres
1200 litres`
12000 litres
120000 litres


Answer

 Option

Capacity of the bank = Volume of the tank = (8*100*6*100*2.5*100 ⁄ 1000) litres = 120000 litres.

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23.  The edge of a cuboid are in the ratio 1 : 2 : 3 and its surface area is 88 cm2. The volume of the cuboid is :


24 cm3
48 cm3
64 cm3
120 cm3


Answer

 Option

Let the dimensions of the cuboid be x, 2x and 3x Then, 2( x * 2x + 2x * 3x + x * 3x) = 88. 2x2 + 6x2 + 3x2 = 11x2 = 44 = x2 = 4 = x = 2. Volume of the cuboid = (2 * 4 * 6) cm3 = 48 cm3

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24.  The height of a wall is six times its width and the length of the wall is seven times its height. If volume of the wall be 16128 cu. m, its width is :


4 m
4.5 m
5 m
6 m


Answer

 Option

Let the width of the wall be x metres. Then, height = (6x) metres and length = (42x) metres. = 42x * x * 6x = 16128 = x3 = (1612842 * 6) = 64 = x = 4.

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25.  The maximum length of a pencil that can be kept in a rectangular box of dimensions 8 cm * 6 cm * 2 cm is :


213 cm
214 cm
226 cm
102 cm


Answer

 Option

Required length = 82 + 62 + 22 cm = 104 cm = 226 cm.

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