Question

A train covers a certain distance at a speed of 12 km/h and the next same distance with a speed of 21 km/h and the next same distance with a speed of 36 km/h. find the average speed?

A 12.6 km/hr Correct Answer Incorrect Answer
B 30 km/hr Correct Answer Incorrect Answer
C 45 km/hr Correct Answer Incorrect Answer
D 18.9 km/hr Correct Answer Incorrect Answer

Solution

Since the distance is same in all the conditions. Therefore, Average speed = 3xyz/(xy + yz + zx) Average speed = 3 x 12 x 21 x 36/(12 x 21 + 21 x 36 + 12 x 36) Average speed = 3 x 12 x 21 x 36/(252 + 756 + 432) = 27216/1440 = 18.9 km/hr    

Practice Next

Relevant for Exams:

×
×