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

 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 If cost of painting is Rs 12 per sq meter of surface area, how much will it cost to paint all surfaces of a solid right circular cylinder with height of 9 meters and base area of 154 sq meters? यदि पेंटिंग की लागत 12 रुपये प्रति वर्ग मीटर सतह क्षेत्रफल है, तो 9 मीटर की ऊंचाई और 154 वर्ग मीटर के आधार क्षेत्रफल के साथ एक ठोस लंब वर्तुल बेलन की सभी सतहों को पेंट करने में कितना खर्च आएगा? A) Rs. 8448 B) Rs. 9372 C) Rs. 1540 D) Rs. 3180 Correct Answer :Rs. 8448 Explanation :Base area of cylinder = πr2 = 154 r2 = 49 Thus, radius, r = 7 Then, Total Surface Area of cylinder = 2πr(h + r) = 2π*7*(9 + 7) = 2* 22/7 * 7 *(9 + 7) = 704 Hence, Cost of painting = 12 * 704 = Rs 8448 If the volume of a cylinder is 2156 cubic cm and height is 14 cm, find its radius? यदि किसी बेलनाकार वस्तु का आयतन 2156 घन सेमी और ऊँचाई 14 सेमी है, तो इसकी त्रिज्या ज्ञात कीजिए? A) 14 cm B) 21 cm C) 3.5 cm D) 7 cm Correct Answer :7 cm Explanation :h = 14 cm, r = ? Volume = 2156 cm3 πr2h = 2156 22/7 * r2 *14 = 2156 r2 = 2156*7 / 22*14 r2 = 49 r = 7 cm