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

 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 ? A) 64 cm2B) 256 cm2C) 384 cm2D) 512 cm2Correct 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 ? A) √150 cmB) √98 cmC) 3√21 cmD) 3√52 cmCorrect 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 ? A) 7 mB) 10.5 mC) 14 mD) 15 mCorrect 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 ? A) 1 unitB) 2 unitC) 3 unitD) 4 unitCorrect 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 ? A) 2rB) r/3C) 4rD) (2/3)rCorrect 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 A hall is 12m long and 8m broad. If the sum of the area of the floor and the ceiling is equal to the sum of the area of the four walls. Find the height of the hall (in m) A) 4.8 B) 6.4 C) 8.3 D) 3.2 Correct Answer :4.8 Explanation :Area of 4 walls of a room = (l*h)+(b*h)+(l*h)+(b*h) =2(l*h)+2(b*h) = 2h(l+b) Area of the floor + Area of ceiling =>(l*b) +(l*b) => 2*(l*b) We have, Area of 4 walls of a room= Area of the floor + Area of ceiling Hence, 2 * h*(12 + 8) = 2*(12 * 8) h = 96/20 = 4.8 m If each side of a cube is 3 centimeter,then its surface area is : यदि किसी घन का प्रत्येक भुजा 3 सेंटीमीटर है, तो उसका पृष्ठीय क्षेत्रफल है: A) 54 Cubic Centimeter B) 9 Square Centimeter C) 54 Square Centimeter D) None of these Correct Answer :54 Square Centimeter Explanation :if side of the square as “a”, then Surface area of a cube = 6a2 = 6*(3)2 = 54 cm2 A 5 cm cube is cut into as many 1 cm cubes as possible. What is the ratio of the surface area of the larger cube to the smaller cubes? एक 5 सेमी का घन(क्यूब) को यथासंभव 1 सेमी घन में काटा जाता है। बड़े घन के सतह क्षेत्र का अनुपात छोटे घन के सतह क्षेत्रो के योग का क्या अनुपात है? A) 1/6 B) 1/5 C) 1/25 D) 1/125 Correct Answer :1/5 Explanation :The volume of the original cube = 53 = 125 cm3. The volume of a smaller cubes = 13 = 1 cm3. Therefore, we will be get total smaller cubes = 125/1 = 125 The surface area of the larger cube = 6*a2 = 6(52) = 6 * 25 = 150 The surface area of each of the smaller cubes = 6 (12) = 6. Therefore, surface area of all of the 125, 1 cm3 cubes = 125 * 6 = 750. Hence, the required ratio = 150 / 750 = 1 / 5 If the surface area of sphere is 346.5 cm2, then its radius is [ taking π=22/7 ]? यदि गोले का सतह क्षेत्र 346.5 cm2 है, तो इसका त्रिज्या है [π = 22/7] ? A) 5.25 cm B) 7.25 cm C) 3.25 cm D) 9.25 cm Correct Answer :5.25 cm Explanation :Surface area of sphere= 4πr2 4 * 22/7 * r2 = 346.5 r2 = 346.5 * 7 / 4 * 22 = 27.5625 r = √27.5625 = 5.25 cm