To cover a distance of 15 km B takes 30 min more than of A. If B doubles his speed then he will cover the same distance in 1 hour less than A. Find the speed of A? 15 किलोमीटर की दूरी तय करने मे B को A से 30 मिनट अधिक लगते हैं । यदि B अपनी गति को दोगुना कर दे तो उसे उसी दूरी को तय करने में A से 1 घंटे कम लगेंगे । A की चाल ज्ञात कीजिए?

Let A's speed be 'a' kmph and B's speed be 'b' kmph. Time taken by A = 15/a hours. Time taken by B = 15/b hours. First condition: 15/b = 15/a + 0.5 (30 min = 0.5 hour). Second condition: 15/(2b) = 15/a - 1 (1 hour less). From first equation: 15/a = 15/b - 0.5. Substituting in second: 15/(2b) = (15/b - 0.5) - 1 = 15/b - 1.5. Solving: 15/(2b) = 15/b - 1.5, so 7.5/b = 15/b - 1.5, giving 1.5 = 7.5/b, so b = 5 kmph. Then 15/a = 15/5 - 0.5 = 2.5, so a = 15/2.5 = 6 kmph.