Two cars A and B started from point X & Y respectively, and the distance between these two points is 660 km. Both cars started at 10 AM and meet at 3 PM. If speed of car A is 12 km/hr more than that of B, then find the speed of car A (in km/hr)?

Explanation

Information Given: Distance between X and Y = 660 km Both cars started at 10 AM and meet at 3 PM (so, time taken = 5 hours) Speed of A is 12 km/hr more than speed of B Concept/Formula: Relative Speed when moving towards each other (opposite directions) = Speed of A + Speed of B Distance = Relative Speed × Time Let speed of B = x km/hr, so speed of A = x + 12 km/hr Explanation: Total time taken to meet = 5 hours So, (x + x + 12) × 5 = 660 (2x + 12) × 5 = 660 2x + 12 = 132 2x = 120 x = 60 Speed of A = x + 12 = 60 + 12 = 72 km/hr Short Trick: Sum speeds = 660/5 = 132 So, 2x + 12 = 132 (x is speed of car B) x + 6 = 66 x = 60 Speed of A = 72 km/hr