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 circumference of a circular base of Cylinder is 44 cm and its hight is 15 cm. Then the volume of the cylinder is?

A) 2759 cub. cm B) 2247 cub. cm
C) 2614 cub. cm D) 2311 cub. cm
 
Answer & Explanation Answer: D) 2311 cub. cm

Explanation:

Given Circumference of a circular base of a cylinder = 44 cm

We know that Circumference of a circle = 2πr = 44r = 22π

Now given the height of a cylinder h = 15 cm

Volume of a cylinder V = πr2h = π22π215 = 22 x 22 x 153.14 = 2311 cm3.

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23 5943
Q:

An error 2% in excess is made while measuring the side of a square. The percentage of error in the calculated area of the square is:

A) 2% B) 2.02%
C) 4% D) .4.04%
 
Answer & Explanation Answer: D) .4.04%

Explanation:

100 cm is read as 102 cm.

 A1 = (100 x 100)  and A2 =(102 x 102)   

(A2 - A1) = [(102 x 102)-(100 x 100) ]= 404    

Percentage error =[404/(100 x 100 )] x 100%= 4.04%

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1 5917
Q:

The ratio between the perimeter and the breadth of a rectangle is 5 : 1. If the area of the rectangle is 216 sq. cm, what is the length of the rectangle?

A) 16cm B) 18cm
C) 24cm D) .Data inadequate
 
Answer & Explanation Answer: B) 18cm

Explanation:

2(l+b)/b = 5/1 

=> 2l + 2b = 5b  

=> 3b = 2l  

=> b =(2/3) x l

 Then, Area = 216 sq.cm 

 

l x b = 216  

=> l x [(2/3)x l] =216  

=> l x l = 324 

=> l = 18 cm.

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0 5783
Q:

One side of a triangle has length 8 and a second side has length 5. Which of the following could be the area of the triangle?

A) 24 B) 20
C) 26 D) 34
 
Answer & Explanation Answer: B) 20

Explanation:

The maximum area of the triangle will come when the given sides are placed at right angles. If we take 8 as the base and 5 as the height the area = ½ x 8 x 5=20

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2 5757
Q:

A towel, when bleached, was found to have lost 20% of its length and 10% of its breadth. The percentage of decrease in area is:

A) 10% B) 10.08%
C) 20% D) 28%
 
Answer & Explanation Answer: D) 28%

Explanation:

Let original length = x and original breadth = y. 

 

Decrease in area = xy -[(80/100x) * (90/100y)]  

=[(xy-(18/25)xy)]

=(7/25)xy

Decrease % =[(7/25)xy * (1/xy) * 100] =28%

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2 5706
Q:

A tank is 25 m long, 12 m wide and 6 m deep. The cost of plastering its walls and bottom at 75 paise per sq. m, is:

A) Rs. 456 B) Rs. 458
C) Rs. 558 D) Rs. 568
 
Answer & Explanation Answer: C) Rs. 558

Explanation:

Area to be plastered= [2(l + b) x h] + (l x b)

= [2(25 + 12) x 6] + (25 x 12)  

= (444 + 300)  

= 744 

 

Cost of plastering = Rs. 744 x (75/100)= Rs. 558

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1 5605
Q:

Ratio between heights of two cylinder in the ratio 3:5. Their volumes are in the ratio 27:80. Find ratio between their radius ?

A) 1:3 B) 2:1
C) 3:4 D) 4:7
 
Answer & Explanation Answer: C) 3:4

Explanation:

bank

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14 5406
Q:

A Conical tent was erected by the army at a base camp with height 3 m and base diameter 10 m. If every person requires 3.92 cu.m air, then how many persons can be seated in that tent approximately?

A) 20 B) 19
C) 17 D) 22
 
Answer & Explanation Answer: A) 20

Explanation:

Given height of the conical tent = 3 m

Diameter = 10 => Radius = D/2 = 10/2 = 5 m 

Now, as the tent is in the conical form

Volume of the conical tent = πr2h3 

=> (22 x 5 x 5 x 3) / (7 x 3) 

= 22 x 25/7 

= 78.54 cu.m 

Given each person requires 3.92 cu.m of air 

=> Number of persons can be seated in the tent = 78.54/3.92 = 20.03 =~ 20

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17 5355