Solution: 
The base of the cylindrical glass has a radius = 3 cm 
Area of the base will be πr²= 9π cm² 
Volume of the cylindrical glass = πr²h 
The height of the cylindrical glass = v/πr² = 108π/9π = 12 cm. 
The correct option is (A).
(a) 24 cm² (b) 24cm³ 
(c) 120 cm² (d) 120cm³
Solution: 
Length of the cuboidal gift box = 6cm 
Width of the cuboidal gift box = 4cm 
Height of the cuboidal gift box = 5cm 
The volume of the gift box = length × width × height 
= 6cm*4cm*5cm = 120cm³. 
The correct option is (d).
(a) 800dm (b) 800dm² 
(c) 800dm³ (d) 800m
Solution: 
Length (l) of the rectangular prism = 10 dm 
Width (w) of the rectangular prism = 4 dm 
Height (h) of the rectangular prism = 2 m 
= 2 × 10 dm [10 dm = 1 m] =20dm 
Volume of the prism = l × w × h 
10dm*4dm*20dm 
= 800dm³. 
The correct option is (c).
(a) 1:1 (b) 3:1 
(c) 4:9 (d) 9:1
Solution: 
Since the cone and the cylinder have the same base area, their radii are the 
same. 
Therefore, let radius of cone = radius of cylinder= r 
Let h1 and h2 be the height of the cone and the cylinder respectively. 
Therefore, volume of the cone= 1/3πr²h1 
Volume of the cylinder = πr²h2 
It is given that the volumes of the cone and the cylinder are equal 
Therefore, 1/3πr²h1= πr²h2 
 h1= 3h2 => h1/h2 = 3/1 
 Thus, the ratio of the heights of the cone and the cylinder is 3:1. 
 The correct option is (b).
(a) 150cm² (b) 290cm² 
(c) 300cm² (d) 580cm²
Solution: 
The total area to be painted=the surface area of the rectangular box 
= 2(lb + bh + lh). 
= 2(10×5 + 5×16 + 10×16). 
= 2( 50+ 80+160) = 580cm². 
The correct option is (d).
(a) 32cm³ (b) 36cm³ 
(c) 42cm³ (d) 46cm³
Solution: 
Length of each side of small cube = 1 cm 
Volume of each cube = 1 cm3 
The given rectangular prism is made up of 36 small equal sized cubes. 
Volume of 36 cubes = 36 × 1 = 36 cm3 
Volume of the rectangular prism = volume of 36 cubes = 36 cm3. 
The correct option is (b).
(a) 14cm (b) 12cm 
(c) 7cm (d) 6cm
Solution: 
Let the length of the edge of the cube be ‘a’. 
It is known that volume of cube = (edge)³ 
Therefore, (a)³ = 2744cm³ 
 a = ³√2744cm 
 a = ³√2×2×2×7×7×7cm 
 a = 2×7cm = 14cm. 
The correct option is (a).
This is a simple question so students 
should try it self.
The volume of the box, so formed is 
(a) 50cm³ (b) 60cm³ 
(c) 70cm³ (d) 80cm³
Solution: 
Volume of 1 cube = 8 cm3 
Number of cubes joined together to form the box = 10 
Thus, volume of 10 cubes = 10 × 8 cm3 = 80 cm3 
Thus, volume of the box = volume of 10 cubes = 80 cm3 
The correct answer is (d).
THE END.

Surface area and volumes

  • 3.
    Solution: The baseof the cylindrical glass has a radius = 3 cm Area of the base will be πr²= 9π cm² Volume of the cylindrical glass = πr²h The height of the cylindrical glass = v/πr² = 108π/9π = 12 cm. The correct option is (A).
  • 4.
    (a) 24 cm²(b) 24cm³ (c) 120 cm² (d) 120cm³
  • 5.
    Solution: Length ofthe cuboidal gift box = 6cm Width of the cuboidal gift box = 4cm Height of the cuboidal gift box = 5cm The volume of the gift box = length × width × height = 6cm*4cm*5cm = 120cm³. The correct option is (d).
  • 6.
    (a) 800dm (b)800dm² (c) 800dm³ (d) 800m
  • 7.
    Solution: Length (l)of the rectangular prism = 10 dm Width (w) of the rectangular prism = 4 dm Height (h) of the rectangular prism = 2 m = 2 × 10 dm [10 dm = 1 m] =20dm Volume of the prism = l × w × h 10dm*4dm*20dm = 800dm³. The correct option is (c).
  • 8.
    (a) 1:1 (b)3:1 (c) 4:9 (d) 9:1
  • 9.
    Solution: Since thecone and the cylinder have the same base area, their radii are the same. Therefore, let radius of cone = radius of cylinder= r Let h1 and h2 be the height of the cone and the cylinder respectively. Therefore, volume of the cone= 1/3πr²h1 Volume of the cylinder = πr²h2 It is given that the volumes of the cone and the cylinder are equal Therefore, 1/3πr²h1= πr²h2  h1= 3h2 => h1/h2 = 3/1  Thus, the ratio of the heights of the cone and the cylinder is 3:1.  The correct option is (b).
  • 10.
    (a) 150cm² (b)290cm² (c) 300cm² (d) 580cm²
  • 11.
    Solution: The totalarea to be painted=the surface area of the rectangular box = 2(lb + bh + lh). = 2(10×5 + 5×16 + 10×16). = 2( 50+ 80+160) = 580cm². The correct option is (d).
  • 12.
    (a) 32cm³ (b)36cm³ (c) 42cm³ (d) 46cm³
  • 13.
    Solution: Length ofeach side of small cube = 1 cm Volume of each cube = 1 cm3 The given rectangular prism is made up of 36 small equal sized cubes. Volume of 36 cubes = 36 × 1 = 36 cm3 Volume of the rectangular prism = volume of 36 cubes = 36 cm3. The correct option is (b).
  • 14.
    (a) 14cm (b)12cm (c) 7cm (d) 6cm
  • 15.
    Solution: Let thelength of the edge of the cube be ‘a’. It is known that volume of cube = (edge)³ Therefore, (a)³ = 2744cm³  a = ³√2744cm  a = ³√2×2×2×7×7×7cm  a = 2×7cm = 14cm. The correct option is (a).
  • 17.
    This is asimple question so students should try it self.
  • 18.
    The volume ofthe box, so formed is (a) 50cm³ (b) 60cm³ (c) 70cm³ (d) 80cm³
  • 19.
    Solution: Volume of1 cube = 8 cm3 Number of cubes joined together to form the box = 10 Thus, volume of 10 cubes = 10 × 8 cm3 = 80 cm3 Thus, volume of the box = volume of 10 cubes = 80 cm3 The correct answer is (d).
  • 20.