Volume and Surface Area of Solid Figures


  1. Water flows at the rate of 10 m/min from a cylindrical pipe 5 mm in diameter. How long will it take to fill up a conical vessel whose diameter at the base is 40 cm and depth is 24 cm ?









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    Given, radius of pipe 5/2 x 10 = 5/20 cm [∵ 1 cm = 10 mm]
    Height of pipe = 1000 cm
    Radius of vessel = 20 cm and height = 24 cm
    Volume of water flow in one minute from cylindrical pipe = π (5/20)2 x 1000
    = 125/2 π cm3
    and volume of conical vessel = 1/3 π(20)2 x 24 = 3200π cm3
    ∴ Required time = (3200π x 2) / 125π

    Correct Option: A

    Given, radius of pipe 5/2 x 10 = 5/20 cm [∵ 1 cm = 10 mm]
    Height of pipe = 1000 cm
    Radius of vessel = 20 cm and height = 24 cm
    Volume of water flow in one minute from cylindrical pipe = π (5/20)2 x 1000
    = 125/2 π cm3
    and volume of conical vessel = 1/3 π(20)2 x 24 = 3200π cm3
    ∴ Required time = (3200π x 2) / 125π
    = 511/5 or 51 min 12 s


  1. A cylindrical jar, whose base has a radius of 15 cm, is filled with water upto a height of 20 cm, A solid iron spherical ball of radius 10 cm is dropped in the jar to submerge completely in water. Find the increase in the level of water (in cm). ?









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    Let level of water will be increased by h cm
    π x (15)2 x h = (4/3)π(10)3

    Correct Option: D

    Let level of water will be increased by h cm
    π x (15)2 x h = (4/3)π(10)3
    ∴ h = [(4/3) x 10 x 10 x 10] / [15 x 15]
    = 525/27 cm



  1. A conical flask is full of water. The flask has base radius r and height h, This water is poured into a cylindrical flask of base radius mr. The height of water in the cylindrical flask is ?









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    Volume of water = Volume of conical flask = (1/3)πr2h
    Now, the water is poured into cylindrical flask.
    ∴ Volume of cylinder = Volumes of water
    ⇒ π (mr)2 x Height = (1/3)πr2h

    Correct Option: C

    Volume of water = Volume of conical flask = (1/3)πr2h
    Now, the water is poured into cylindrical flask.
    ∴ Volume of cylinder = Volumes of water
    ⇒ π (mr)2 x Height = (1/3)πr2h
    ∴ Height = h/3m2


  1. A hemispherical basin of 150 cm diameter holds water 120 times as much as a cylindrical tube. If the height of the tube is 15 cm, then the diameter of the tube is ?









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    Given, diameter = 150 cm
    ∴ r = 150/2 cm
    According to the question,
    2/3π (150/2)3 = 120 πr2 x 15

    Correct Option: C

    Given, diameter = 150 cm
    ∴ r = 150/2 cm
    According to the question,
    2/3π (150/2)3 = 120 πr2 x 15
    ⇒ (2/3) x 150 x 150 x 150 / 8 = 120 x 15 x r2
    ⇒ r2 = (150 x 150 x 150) / (12 x 120 x 5)
    ⇒ r2 = 625/4
    ⇒ r = √625/4 = 25/2
    ∴ Diameter = 2r = 2 x 25/2 = 25 cm



  1. A copper sphere of diameter 36 cm is drawn into a wire of diameter 4 mm. Find the length of the wire. ?









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    Let length of the wire be h According to the question,
    Volume of sphere = Volume of wire
    (4/3) x π x 18 x 18 x 18 = π x (2/10) x (2/10) x h

    Correct Option: D

    Let length of the wire be h According to the question,
    Volume of sphere = Volume of wire
    (4/3) x π x 18 x 18 x 18 = π x (2/10) x (2/10) x h
    ∴ h = (100 x 1944) cm
    = (100 x 1944)/100 m = 1944 m [∵ 1 cm = 1/100 m]