A car covers three successive 10 km stretches at speeds of 20 km/h, 30 km/h and 60 km/h respectively. Find its average speed. MCQ with Answer and Explanation

Explanation:
New speed = 8/9 of usual speed => New time = 9/8 of usual time. Difference = 1/8 of usual time = 12 minutes. Usual time = 12 * 8 = 96 minutes.

Explanation:
Train 1 takes 4 hours, Train 2 takes 3.5 hours (7/2 hours). Let distance be LCM(4, 3.5) = 28 units. Speed of Train 1 = 7 units/h, Speed of Train 2 = 8 units/h. By 8:00 AM, Train 1 travels 2 hours * 7 = 14 units. Remaining distance = 28 - 14 = 14 units. Relative speed = 7 + 8 = 15 units/h. Time to meet after 8 AM = 14/15 hours = 56 minutes. Meeting time = 8:56 AM.

Explanation:
Speed of express train = 450 / 5 = 90 km/h. Speed of local train = 90 / 2 = 45 km/h. Time taken by local train = 360 / 45 = 8 hours.