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Mensuration-3D Test 217
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Mensuration-3D Test 217
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  • Question 1/10
    1 / -0.25

    220 articles dropped in a water tank which is 52 m long and 47 m broad. If the average displacement of water by an article in 4.5 m3, then approximate rise in the water level will be:
    Solutions

    Let the rise in water level in the tank is x.

    According to the question,

    Total displacement of 220 Articles = Increase in level of Water in tank

    220 × 4.5 × 100= 52 × 47 × x; (Since 1m = 100cm)

    x = 40.5 cm

  • Question 2/10
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    The sum of the radii of spheres A and B is 14 cm, the radius of A being larger than that of B. The difference between their surface areas is 112π. What is the ratio of the volumes of A and B?
    Solutions

    Given:

    ra + rb = 14 cm      …(i)

    4π(ra2 – rb2) = 112π

    (ra – rb)(ra + rb) = 28

    (ra – rb) =  = 2      …(ii)

    On adding Equation (i) and (ii):

    2ra = 14 + 2 = 16

    ra =  = 8 cm

    Now, rb = 14 – 8 = 6 cm

    Now, ratio of volumes of A and B =

    83 : 63

    512 : 216

    64 : 27

  • Question 3/10
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    A solid metallic cuboid of dimensions 18 cm × 36 cm × 72 cm is melted and recast into 8 cubes of the same volume. What is the ratio of the total surface area of the cuboid to the sum of the lateral surface areas of all 8 cubes?
    Solutions

    Volume of a cube = = = 5832

    Side of a cube =  = 18 cm

    Total Surface Area of the cuboid = 2 × 18 × 36 + 2 × 36 × 72 + 2 × 18 × 72

    = 1296 + 5184 + 2592 = 9072 cm2

    Since, a cube has 4 lateral surfaces.

    Then, Lateral Surface Area of all 8 cubes with side length as 18 cm = 8 × 4 × 182 = 10368 cm2

    Required ratio = 9072 : 10368 = 7 : 8

  • Question 4/10
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    The areas of three adjacent faces of a cuboid are 18 cm2, 20 cm2 and 40 cm2. What is the volume (in cm3) of the cuboid?
    Solutions

    Area of three adjacent faces of a cuboid are 18 cm2, 20 cm2 and 40 cm2.

    Then let the length be denoted by l , breadth by b and height be h

    Then l × b = 18

    b × h = 20

    h × l = 40

    then multiplying the above equations :

    (lbh)2 = 18 × 20 × 40

    = 144 × 100

    lbh = 12 × 10

    volume = lbh = 120 cm3

  • Question 5/10
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    A conical tent has to accommodate 25 persons. Each person must have 4 m2 of space of the ground and 80 m3 of air to breathe. Find the height of the tent.
    Solutions

    Required, Area of Base = 25 × 4 = 100 m2

    Required Volume = 25 × 80 = 2000 m3

    Volume of the conical tent = () × Area of base × height = 2000

    ⇒ Height =  = 60 m

  • Question 6/10
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    The volume of prism is 288 cm and height is 24 cm. The base area (in cm) of the prism is:
    Solutions

    Given that,

    Volume of the prism= 288 cm3

    Height of the prism = 24 cm.

    We know that,

    The volume of a Prism = Base area of prismHeight

    Where,

    Therefore,

    288 = Base area of prism 24

    Base area of prism =

    Base area of prism = 12 cm.

    Therefore, option D is the right answer.

  • Question 7/10
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    The base of a right pyramid is a square of side 10 cm. If its height is 10 cm, then the area (in cm2) of its lateral surface is:
    Solutions

    Lateral height of pyramid with base as a square =

    = =  = 5√5 cm

    Lateral surface area of pyramid =

    =  = 100√5 cm2

  • Question 8/10
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    Let A and B be two cylinders such that the capacity of A is the same as the capacity of B. The ratio of the diameters of A and B is 1 : 4. What is the ratio of the heights of A and B?
    Solutions

    Ratio of r1 : r2 = 1 : 4 (ratio of the diameters of A and B is 1 : 4)

    r2 = 4r1

    Given:

    Volume of cylinder A = Volume of cylinder B

    πr12h1 = πr22h2

    r12h1 = (4r1)2h2

    h1 = 16h2

    h1 / h2 = 16 / 1

    Therefore, h1 : h2 = 16 : 1

  • Question 9/10
    1 / -0.25

    A hollow iron pipe is 10 cm long and its external diameter is 18cm. If the thickness of the pipe is 2cm and iron weighs 8.5 g/cm3, then the weight of the pipe from the following is closest to:
    Solutions

    Here, External diameter= 18 cm

    So external radius(R) = 18/2 = 9 cm

    Internal radius(r) = (9 – 2) = 7 cm

    Volume of a hollo pipe = πh(R2 – r2)

    = 3.14 × 10 × (92 – 72)

    = 31.4 × (81 – 49)

    = 31.4 × 32 = 1004.8 cm3

    Weight of the hollow pipe (in Kg) = 1004.8 × 8.5/1000

    = 8.54 kg

  • Question 10/10
    1 / -0.25

    From solid cylinder with base diameter 14 cm and height 20 cm, hemispherical parts of radius 7 cm were cut from both the ends of the cylinder. Find the volume of the resultant object?
    Solutions

    Volume of solid cylinder = πr2h; (r=radius and h=height)

    Volume of hemi-sphere = πr3

    Since hemi-spheres are cut from both ends,

    Total volume cut out = 2 × πr3 = πr3

    Now, required volume of the resultant object will be

    = πr2h − πr3

    = πr2(h – 4r/3)

    = ; (h = 20 cm and diameter = 14 cm)

    =

    = 22×7×32/3

    =

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