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All questions of Surface Area & Volumes for EmSAT Achieve Exam

A rectangular sand box is 5 m wide and 2 m long. How many cubic metres of sand are needed to fill the box upto a depth of 10 cm ?
  • a)
    1
  • b)
    10
  • c)
    100
  • d)
    1000
Correct answer is option 'A'. Can you explain this answer?

To calculate the volume of sand needed to fill the rectangular sandbox, we can use the formula:Volume = Length × Width × DepthGiven:
Length = 2 m
Width = 5 m
Depth = 10 cm = 0.1 mSubstituting the values into the formula:Volume = 2 m × 5 m × 0.1 m
Volume = 1 cubic meterTherefore, the correct answer is A: 1 cubic meter.

If the lateral surface area of a cube is 1600 cm2, then its edge is:
  • a)
    20 cm
  • b)
    15 cm
  • c)
    18 cm
  • d)
    25 cm
Correct answer is option 'A'. Can you explain this answer?

Anchal Singh answered
Lateral surface area is the surface area of an object excluding it's base and top. A cube has 6 faces, subtracting the base and top is 4. 
1600 / 4 = 400 so each side has an area of 400 cm squared.
 The square root of 400 is 20 so the edge of the cube is 20 cm.

A conical tomb of base diameter 24m and height 16 m. What is the curved surface area?
  • a)
    200π sq m
  • b)
    240π sq m
  • c)
    300π sq m
  • d)
    64π sq m
Correct answer is option 'B'. Can you explain this answer?

Sagnik Menon answered
The formula for the curved surface area of a cone is πrs, where r is the radius of the base and s is the slant height. To find the slant height, we can use the Pythagorean theorem: s² = r² + h², where h is the height of the cone.

In this case, the radius is half of the base diameter, so r = 12m. Using the Pythagorean theorem, we get:

s² = 12² + 16²
s² = 144 + 256
s² = 400
s = 20m

Now we can calculate the curved surface area:

A = πrs
A = π(12)(20)
A = 240π

Using a calculator, we can approximate this to:

A ≈ 753.98

Therefore, the curved surface area of the conical tomb is approximately 753.98 square meters.

A beam 9 m long, 40 cm wide and 20 cm deep is made up of iron which weighs 50 kg per cubic metre.
The weight of the beam is :
  • a)
    27 kg
  • b)
    36 kg
  • c)
    48 kg 
  • d)
    56 kg
Correct answer is option 'B'. Can you explain this answer?

To find the weight of the iron beam, we need to calculate its volume and then multiply it by the weight of 1 cubic meter of iron, which is given as 50 kg.Given:
Length of beam (l) = 9 m
Breadth (b) = 40 cm = 0.4 m
Height (h) = 20 cm = 0.2 m
Weight of 1 cubic meter of iron = 50 kgVolume of the beam = l × b × h = 9 m × 0.4 m × 0.2 m = 0.72 cubic metersWeight of the beam = Volume × Weight of 1 cubic meter of iron = 0.72 cubic meters × 50 kg/cubic meter = 36 kg
Therefore, the weight of the iron beam is 36 kg, which corresponds to option B.

The surface area of a cube of edge 1.5 cm is​
  • a)
    9.50 cm2
  • b)
    9 cm2
  • c)
    15.50 cm2
  • d)
    13.50 cm2
Correct answer is option 'D'. Can you explain this answer?

Surface area of cube =6a^2
surface area of cube=6×(1.5)^2
surface area of cube=6×2.25
surface area of cube=13.50 answer...

The surface area of a cube of side 27 cm is :
  • a)
    2916 cm2
  • b)
    729 cm2
  • c)
    4374 cm2
  • d)
    19683 cm2
Correct answer is option 'C'. Can you explain this answer?

The surface area of a cube of side 27 cm can be found using the formula:Surface area of a cube = 6a^2, where a is the length of the side of the cube.Given:
Length of side of the cube = 27 cmSubstituting the value into the formula:Surface area of the cube = 6 × 27^2
Surface area of the cube = 6 × 729
Surface area of the cube = 4374 cm^2Therefore, the surface area of the cube of side 27 cm is 4374 cm^2, which corresponds to option C

The radius of two similar right circular cones are 2 cm and 6 cm. The ratio of their volumes is
  • a)
    1 : 3
  • b)
    1 : 9
  • c)
    9 : 1
  • d)
    1 : 27
Correct answer is option 'D'. Can you explain this answer?

Let the volume two cones be v1 & v2 & r1 and r2 be the radii of the two right circular cones & height of the two cones be h.

Ratio of base radii = r1:r2= 3 : 5

Volume of cone = 1/3πr^2h

Volume of first cone (v1)1/Volume of second cone (v2)

=(1/3�π�r1^2�h)/(1/3�π�r2^2�h)

= (1/3�π�3^2�h)/(1/3�π�5^2�h)

= r1^2/r2^2

= 3^2/5^2

= 9/25

= 9 : 25
Hence, the ratio of their volumes is 9 : 25

The cost of cementing the inner curved surface of a 14 m deep well of radius 2 m at the rate of Rs 2 per m2 is
  • a)
    Rs 352.
  • b)
    Rs 176.
  • c)
    Rs 56.
  • d)
    Rs 112.
Correct answer is option 'A'. Can you explain this answer?

Depth of well(h) = 14m
radius of well(r) = 2m
Inner surface area of well(like a cylinder) = 2πrh 
surface area= 2 x 22/7 x 2 x 14 = 176 m2
cost of cementing = ₹2 per m2
Total Cost = 176 x 2 = ₹352

If the ratio of volumes of two spheres is 1 : 8, then the ratio of their surface areas is :
  • a)
    1 : 2
  • b)
    1 : 4
  • c)
    1 : 8
  • d)
    1 : 16
Correct answer is option 'B'. Can you explain this answer?

Sarita Reddy answered
The correct answer is option 'B', the ratio of surface areas is 1:4.
The ratio of the surface areas of two spheres is the square of the ratio of their radii. If the ratio of volumes of two spheres is 1:8, then the ratio of their radii is 3:2 . Therefore, the ratio of the surface areas of the two spheres is (3/2)^2 = 9/4 = 1:4

The volume of a spherical shell whose internal and external diameters are 8 cm and 10 cm respectively (in cubic cm) is:
  • a)
    122π/3
  • b)
    244π/3
  • c)
    212
  • d)
    257
Correct answer is option 'B'. Can you explain this answer?

Sarita Reddy answered
The volume of a spherical shell is the difference between the volumes of the two spheres that make up the shell. The internal sphere has a diameter of 8 cm, and the external sphere has a diameter of 10 cm. To find the volume of the spherical shell, we can first find the volume of each of the two spheres and then subtract the volume of the smaller sphere from the volume of the larger sphere.
The volume of a sphere is given by the formula V = (4/3)πr^3, where V is the volume, r is the radius of the sphere, and π is a mathematical constant approximately equal to 3.14159. The radius of the internal sphere is 4 cm (half of the diameter), and the radius of the external sphere is 5 cm (half of the diameter). Therefore, the volume of the internal sphere is (4/3)π(4^3) = (4/3)π64 = 256π/3 cubic cm, and the volume of the external sphere is (4/3)π(5^3) = (4/3)π125 = 500π/3 cubic cm.
To find the volume of the spherical shell, we subtract the volume of the internal sphere from the volume of the external sphere: 500π/3 - 256π/3 = 244π/3 cubic cm. Therefore, the volume of the spherical shell is 244π/3 cubic cm, which corresponds to answer choice (b).

The total surface area of a hemispherical bowl of diameter 28 cm is​
  • a)
    1848 cm2
  • b)
    1800 cm2
  • c)
    1600 cm2
  • d)
    1648 cm2
Correct answer is option 'A'. Can you explain this answer?

Sarita Reddy answered
Correct, option 'A' is the correct answer.
The total surface area of a hemispherical bowl can be calculated by using the formula 4πr^2, where r is the radius of the bowl.
Given the diameter of the bowl is 28 cm, the radius of the bowl is 14cm.
So, the total surface area of the hemispherical bowl of diameter 28 cm is 4π(14)^2 = 4π*196 =784π = 1848 cm^2 (approximately)
Alternatively, we can also use the formula 2πr^2 + 2πrr (r being the radius of the bowl) to calculate the total surface area of the hemispherical bowl.
In this case, 2π(14)^2 + 2π(14) 14 = 2π196 + 2π196 = 392π = 1848 cm^2 (approximately)
Hence the answer is A. 1848 cm2

If a hemi-spherical dome has an inner diameter of 28 m, then its volume (in m3) is :
  • a)
    6186.60
  • b)
    5749.33
  • c)
    7099.33
  • d)
    7459.33
Correct answer is option 'B'. Can you explain this answer?

Sarita Reddy answered
Correct, option 'B' is the correct answer.
The volume of a hemisphere can be calculated using the formula, V = 2/3 * π * r^3, where r is the radius of the hemisphere.
A hemi-spherical dome has an inner diameter of 28 m, so the radius of the hemisphere is half of the diameter which is 14m.
So, the volume of the hemi-spherical dome is: 2/3 * π * (14)^3 = 2/3 * π * 2744 = 5749.33 m^3 (approximately)
Hence the answer is B. 5749.33 m^3

A cubical tank has an edge equal to 6 m. The amount of water it will contain when it is one-third filled is
  • a)
    64000 litres
  • b)
    72000 litres
  • c)
    54000 litres
  • d)
    36000 litres
Correct answer is option 'B'. Can you explain this answer?

Nishanth Das answered
Given:
Edge of cubic tank = 6 m
The tank is one-third filled.

To find:
The amount of water in the tank.

Solution:
Volume of the tank = (Edge)^3
= (6)^3
= 216 m^3

The tank is one-third filled.
So, the amount of water in the tank = (1/3) * 216 m^3
= 72 m^3

1 m^3 = 1000 litres
Therefore, 72 m^3 = 72 * 1000 litres
= <72*1000=72000>>72000 litres

Hence, the amount of water in the tank when it is one-third filled is 72000 litres.

Therefore, option (b) is the correct answer.

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