Question:
If the height of a regular right pyramid with a square base is increased by 20% and the side length of its base is decreased by 10%, what is the percentage change in its volume?
यदि एक वर्गाकार आधार वाले सम लंब पिरामिड की ऊंचाई 20% बढ़ा दी जाती है और इसके आधार की भुजा की लंबाई 10% कम कर दी जाती है, तो इसके आयतन में प्रतिशत परिवर्तन क्या होगा?
Options:
- a) 2.8% decrease
- b) 1.2% increase
- c) 2.8% increase
- d) No change
- a) 2.8% कमी
- b) 1.2% वृद्धि
- c) 2.8% वृद्धि
- d) कोई बदलाव नहीं
correct answer : a)
Explanation:
V = (1/3)*a²*h. New a = 0.9a, New h = 1.2h. New V = (1/3)*(0.9a)²*(1.2h) = (1/3)*0.81a²*1.2h = 0.972 * Old V. Change = (1 – 0.972)*100 = 2.8% decrease.
V = (1/3)*a²*h. नया a = 0.9a, नया h = 1.2h. नया V = (1/3)*(0.9a)²*(1.2h) = (1/3)*0.81a²*1.2h = 0.972 * पुराना V. परिवर्तन = (1 – 0.972)*100 = 2.8% कमी।