Volume and Surface Area Questions

FACTS  AND  FORMULAE  FOR  VOLUME  AND  SURFACE  AREA  QUESTIONS

 

 

I. CUBOID

   Let length=l, breadth =b and height =h units. Then,

1. Volume = (l x b x h)

2. Surface area = 2(lb +bh + lh) sq.units

3. Diagonal =l2+b2+h2 units

 

 

II. CUBE 

Let each edge of a cube be of length a. Then,

1. Volume = a3 cubic units.

2. Surface area = 6a2 sq.units

3. Diagonal = 3a units

 

 

III. CYLINDER 

Let radius of base = r and Height (or Length) = h. Then, 

1.Volume = πr2h cubic units 

2. Curved surface area = 2πrh sq.units

3. Total surface area = 2πrh+2πr2 sq.units

 

 

IV. CONE 

Let radius of base =r and Height = h. Then, 

1. Slant height, l=h2+r2 units

 

2. Volume = 13πr2h cubic units.

 

3. Curved surface area = πrlsq.units 

 

4. Total surface area = πrl+πr2sq.units

 

 

V. SPHERE 

Let the radius of the sphere be r. Then, 

1. Volume =43πr3 cubic units

2. Surface area = 4πr2 sq.units

 

 

VI. HEMISPHERE 

Let the radius of a hemisphere be r. Then, 

1. Volume = 23πr3 cubic units.

2. Curved surface area = 2πr2 sq.units

3. Total surface area = 3πr2 sq.units

 

Q:

The diagonal of the floor of a rectangular closet is 712 feet. The shorter side of the closet is 412 feet. What is the area of the closet in square feet?

A) 5 .5 B) 13.5
C) 27 D) 37
 
Answer & Explanation Answer: C) 27

Explanation:

Other side=1522-922ft  =2254-814ft  =1444= 6ft

 

Area of closet =(6 x 4.5)sq.ft = 27 sq.ft 

 

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5 8000
Q:

A rectangular box measures internally 1.6m long, 1m broad and 60cm deep. The number of cubical box each of edge 20cm that can be packed inside the box is:

A) 30 B) 60
C) 90 D) 120
 
Answer & Explanation Answer: D) 120

Explanation:

Number of blocks =160×100×6020×20×20=120

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10 7866
Q:

Consider the following statements:

1) The perimeter of a triangle is greater than the sum of its three medinas.

2) In any triangle ABC, if D is any point on BC, then AB + BC + CA > 2AD.

Which of the above statements is/are correct?

A) 1 only B) 2 only
C) Both 1 and 2 D) Neither 1 nor 2
 
Answer & Explanation Answer: C) Both 1 and 2

Explanation:
Let ABC be the triangle and D. E and F are midpoints of BC, CA and AB respectively.
Recall that the sum of two sides of a triangle is greater than twice the median bisecting the third side,(Theorem to be remembered)
Hence in ΔABD, AD is a median
AB + AC > 2(AD)
Similarly, we get
BC + AC > 2CF
BC + AB > 2BE
On adding the above inequations, we get
(AB + AC) + (BC + AC) + (BC + AB )> 2AD + 2CD + 2BE
2(AB + BC + AC) > 2(AD + BE + CF)
AB + BC + AC > AD + BE +CF
 
2.
To prove: AB + BC + CA > 2AD
Construction: AD is joined
Proof: In triangle ABD,
AB + BD > AD [because, the sum of any two sides of a triangle is always greater than the
third side]
----
1
In triangle ADC,
AC + DC > AD [because, the sum of any two
sides of a tri
angle is always greater than the
third side]
----
2
Adding 1 and 2 we get,
AB + BD + AC + DC > AD + AD
=> AB + (BD + DC) + AC > 2AD
=> AB + BC + AC > 2AD
Hence proved
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1 7737
Q:

A boat having a length 3 m and breadth 2 m is floating on a lake. The boat sinks by 1cm when a man gets on it. The mass of the man is:

A) 12 kg B) 60 kg
C) 72 kg D) 96 kg
 
Answer & Explanation Answer: B) 60 kg

Explanation:

ke

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11 7632
Q:

A rectangular block has the dimensions 5x6x7 cm it is dropped into a cylindrical vessel of radius 6cm and height 10 cm. If the level of the fluid in the cylinder rises by 4 cm, What portion of the block is immersed in the fluid ?

A) 22/7 x 24/35 B) 22/7 x 36 x 4
C) 22/7 x 36/5 D) 22/7 x 37/21
 
Answer & Explanation Answer: A) 22/7 x 24/35

Explanation:

Since level of water increased in cylinder by height 4. 

This is because of the rectangular block .

 

Therefore , area of rectangular block immersed in water is 

= 227×6×6×4  

Thats why portion of block immersed in water is 

= (22/7 * 36 * 4) / total vol. of rectangle 

= (22/7 * 36 * 4)/ (7*5*6) 

= (22/7 * 24)/ 35.

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7 7629
Q:

How many meshes are there in 1 squrare meter of wire gauge if each mesh is 8mm long and 5mm wide ?

A) 2500 B) 25000
C) 12500 D) 15400
 
Answer & Explanation Answer: B) 25000

Explanation:

We know that,

 

One square meter is equal to 10,00,000 sq mm.
Given, each mesh is 8mm length and 5mm wide
Therefore for each mesh : 8 x 5 = 40 sq mm.
So, number of meshes = 100000040 = 25000.

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6 7519
Q:

What is the ratio between the volumes of a cylinder and cone of the same height and of the same diameter

A) 2:1 B) 3:1
C) 4:1 D) 5:1
 
Answer & Explanation Answer: B) 3:1

Explanation:

Volume of cylinder / Volume of cone = 3/1

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1 7193
Q:

88 cubic centimetres of silver is drawn into a wire 1 mm in diameter. The length of the wire in metres will be ?

A) 112 mts B) 84 mts
C) 96 mts D) 108 mts
 
Answer & Explanation Answer: B) 84 mts

Explanation:

Vol of silver = πR2h  = 66 C.C  

Given D= 1mm => R = D/2 = 1/20 cm  

 

=> 227×1202×h = 66

= 66 x 400 x (7/22) = 8400 cm = 84 mtrs.

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8 6968