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 corners of a square of side ‘a’ are cut away so as to form a regular octagon. What is the side of the octagon?

A) a(√2 –1) B) a(√3 –1)
C) a/√2+2 D) a/3
 
Answer & Explanation Answer: A) a(√2 –1)

Explanation:

Since we are forming a regular octagon

so AE = AL = FB = BG and so on

So AE = SB = x/√2

AE + EF + FB = side of square = a (Given)

So x/√2 + x + x/√2 = a

X = a/(√2+1) = a(√2 -1)

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Q:

BD and CE are two medians of the triangle ABC. If EO = 7 cm, then the length of CE is

A) 28 cm B) 14 cm
C) 21 cm D) 35 cm
 
Answer & Explanation Answer: C) 21 cm

Explanation:
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Q:

What is the reflection of the point (-2, 5) in the line x = -1?

A) (-2 , -7) B) (0 , 5)
C) (2 , 5) D) (-2 , 7)
 
Answer & Explanation Answer: B) (0 , 5)

Explanation:
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Q:

If in ΔABC, DE ||BC, AB = 7.5cm, BD = 6cm and DE = 2cm, then the length of BC in cm is

A) 6 B) 8
C) 10 D) 10.5
 
Answer & Explanation Answer: C) 10

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Q:

The height and the total surface area of a right circular cylinder are 4 cm and 8π sq.cm. respectively. The radius of the base of cylinder is

A) (2√2 - 2) cm B) (2 - √2) cm
C) 2 cm D) √2 cm
 
Answer & Explanation Answer: A) (2√2 - 2) cm

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Q:

The midpoints of AB and AC of a triangle ABC are X and Y respectively. If BC+XY=12 units, then BC­XY is

A) 10 units B) 8 units
C) 6 units D) 4 units
 
Answer & Explanation Answer: D) 4 units

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Q:

A sphere has the same curved surface area as a cone of vertical height 40 cm and radius 30 cm. The radius of the sphere is

A) 5√5 cm B) 5√3 cm
C) 5√15 cm D) 5√10 cm
 
Answer & Explanation Answer: C) 5√15 cm

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Q:

The internal bisectors of ∠Q and ∠R of triangle PQR meet at O. If ∠P = 70°, then what is the measure of ∠QOR (in degrees)?

A) 110 B) 115
C) 125 D) 135
 
Answer & Explanation Answer: C) 125

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