Formulae :
Distance = Speed * Time
Rule : If certain distance is covered at x km/hr and the same distance is covered at y km / hr then the average speed during whole journey is :
Ex. Ram can cover a certain distance in 1 hr 30 min. By covering two third of the distance at 4 kmph and the rest at 5 kmph. Find the total distance covered ?
Solution : Let the total distance be x km then:
Ex. Walking at 4 / 5 of its normal speed, a school bus is 10 minutes late. Find its usual time to cover the journey.
Solution : New Speed = 4 / 5 of original speed, since the speed and time has inverse relation so,
New Time taken by bus = 5 / 4 of the normal time
( 5 / 4 of usual time ) - ( usual time ) = 10 min.
1 / 4 of the normal time = 10 min
normal time = 40 min
Ex. The distance between two stations Delhi and Lucknow is 500 km. A train starts at 5 pm from delhi and moves towards Lucknow at an average speed of 50 km / hr, Another train starts at 4.20 pm and moves towards delhi at an average speed of 70 km/hr. How far from delhi the two trains meet and at what time ?
Solution : Let the two trains meets at a distance of x km from delhi.
Now [Time taken by train from Lucknow to cover (500-x)km] - [Time taken by train from delhi to cover x km ] = 40 / 60
Ex. Bullcart A cover a certain distance at the speed of 15 km/hr, another bullcart B covers the same distance at the speed of 16 km/hr. If Bull cart A takes 16 minutes longer than B to cover the same distance find the distance?
Solution : let the distance is x km
Time taken by A= x / 15 hrs
Time taken by B= x / 16 hrs
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