Volume and Surface Area- Aptitude Questions and Answers - in Hindi

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The volume of a right circular cylinder is 392π cm3 and its height is 8 cm. Find the radius?


एक बेलन का आयतन 392π cm3 है और उसकी ऊँचाई 8 cm है। त्रिज्या ज्ञात कीजिए?

A)

6 cm


B)

7 cm


C)

8 cm


D)

9 cm



Correct Answer :

7 cm


Explanation :

Volume of a cylinder = πr2h
392π = π*r2*8
r2 = 392/8
r2 = 49
r = 7 cm

If the height of right circular cylinder is 10 cm and radius of its base is 4 cm, find its total surface area?


यदि एक बेलन की ऊँचाई 10 cm है, और उसके आधार की त्रिज्या 4 cm है, तो उसके सम्‍पर्णू प्रष्‍ठीय क्षेत्र का क्षेत्रफल ज्ञात कीजिए?

A)

350 cm²


B)

351 cm²


C)

352 cm²


D)

353 cm²



Correct Answer :

352 cm²


Explanation :

Total Surface Area of a cylinder= 2πrh + 2πr2 = 2πr(h + r)
= 2* 22/7 * 4 *(10 + 4)
= 2* 22/7 * 4 * 14
= 2* 22 * 4 * 2
= 352 cm2

Length,Width and Height of a cuboid are in the ratio of 6:3:5. If the total surface area of cuboid is 1134 cm2 then find its Length, Width and Height.


एक घनाभ की लंबाई, चौड़ाई और ऊंचाई 6:3:5 के अनुपात में है। यदि घनाभ का सम्पूर्ण पृष्ठ का क्षेत्रफल 1134 वर्ग सेमी है, तो इसकी लंबाई, चौड़ाई और ऊंचाई ज्ञात करें।

A)
18, 9, 15

B)
17, 10, 15

C)
12, 15, 9

D)
11, 13, 16


Correct Answer :

18, 9, 15


Explanation :

Let the length,width and height of the cuboid are 6x,3x,5x respectively.

The total surface area of cuboid ,2*(lb + bh + lh) = 1134
=>2*(6x×3x+3x×5x+6x×5x) = 1134
=>18x2 + 15x2 + 30x2 = 567
=>63x2 = 567
=>x2 = 9
So x=3

Hence the dimensions of cuboid will be 18, 9, 15.

If the surface area of two spheres are in the ratio 9:16, then the ratio of their volumes will be?


यदि दो गोलों के पृष्ठीय क्षेत्रफलों का अनुपात 9 : 16 है , तो उनके आयतनों का अनुपात होगा?

A)

9:16


B)

16:9


C)

27:64


D)

3:4



Correct Answer :

27:64


Explanation :

Let the radius of two sphere be r and R

As is given, 4πr2/4πR2 = 9/16
r2/R2 = 9/16
r/R = 3/4

ratio of their volume = (4πr3/3) / (4πR3/3)
=r3/R3
=(r/R)3
=(3/4)3
=27/64

The volume of a cube is 512 cm3, Its surface area is ?

64 cm2
256 cm2
384 cm2
512 cm2

Correct Answer :

384 cm2


Explanation :

Volume =a3 = 512 cm3= 8 x 8 x 8
⇒ a = 8 cm
Then, Surface area = 6a2
=6 x (8)2 cm2
=384 cm2

A box is of 10 cm long, 8 cm broad and 5 cm high. What is the longest possible length of a pencil that can be put in ?

√150 cm
√98 cm
3√21 cm
3√52 cm

Correct Answer :

3√21 cm


Explanation :

Since, the box is in the form of a cuboid.

longest possible length of a pencil=>diagonal of cuboid=√(l2 +b2 +h2)
= √102 +82 + 52 cm
= √189
= √9 x 21
= 3√21 cm

Find the height of the cylinder whose volume is 551 m3 and the area of the base is 36.5 m2 ?

7 m
10.5 m
14 m
15 m

Correct Answer :

14 m


Explanation :

Base of cylinder => Area of circle = πr2 = 36.5 m2

Volume of cylinder = πr2h = Area base * height = 36.5 * h
551 = 36.5 x h
Hence height of the cylinder, h = 511/36.5 = 14 m

If the volume and surface are of a sphere are numerically the same then its radius is ?

1 unit
2 unit
3 unit
4 unit

Correct Answer :

3 unit


Explanation :

Volume = (4/3)πr3
Surface Area = 4πr2

as per question, 4/3 πr3 = 4πr2
⇒ r = 3 units.

A cylinder and a cone have the same height and same radius of the base. The ratio between the volumes of the cylinder and the cone is ?


एक सिलेंडर और शंकु के समान ऊंचाई और आधार समान त्रिज्या के हैं। सिलेंडर और शंकु के आयतन के बीच अनुपात है

A)
1 : 3

B)
3 : 1

C)
1 : 2

D)
2 : 1


Correct Answer :

3 : 1


Explanation :

Volume of Cylinder = πr2h

Volume of cone = (1/3)πr2h

Ratio of their volumes = [πr2h] / [(1/3)πr2h] => 3/1 => 3 : 1

A sphere of radius r has the same volume as that of a cone with circular base of radius r. Find the height of the cone ?

2r
r/3
4r
(2/3)r

Correct Answer :

4r


Explanation :

Volume of sphere = Volume of cone
⇒ (4/3)πr3 = (1/3)πr2h
⇒ 4r = h

If the volume of the cube is 1331 m3, then the total surface area of the cube is(in m2):

A)
648

B)
484

C)
726

D)
216


Correct Answer :

726


Explanation :

Let the side of Cube is a

Then,
Volume of Cube = a3 =1331 m3
a=11
So Surface Area of the cube is = 6a2 = 6* 112 =6*121
=726

The areas of two circles are in the ratio 1:2. Find the ratio of their radius?

A)
1:2

B)
1:3

C)
1:√2

D)
1:4


Correct Answer :

1:√2


Explanation :

Ratio of the areas of the circles = π(r1)2 : π(r2)2 =1:2
hence, (r1)2 : (r2)2 =1:2
(r1) : (r2) =1:√2

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