Aptitude Time And Distance Tutorials & Tricks

Time And Distance Tutorials & Tricks

Introduction

Time and Distance problem in which a work is done depending on some time constraints.

Formula for finding out Time and Distance

1. Speed, Time and Distance:

Speed = (Distance/Time ),

Time = (Distance/Speed),

Distance = (Speed x Time).

2. km/hr to m/sec conversion:

x km/hr = (x(5/18)) m/sec.

3. m/sec to km/hr conversion:

x m/sec = (x(18/5)) km/hr.

4. If the ratio of the speeds of A and B is a : b, then the ratio of the the times taken by then to cover the same distance is 1/a : 1/b or b : a.

5. Suppose a man covers a certain distance at x km/hr and an equal distance at ykm/hr. Then, the average speed during the whole journey is (2xy/(x+y)) km/hr.

6. Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then, the average speed during the whole journey is 2x/yx+y

Sample Example

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 ?

A

 Let the total distance be x km then: {([(2/3)x]/4) + ([(1/3)x]/5)} = 1+(1/2) = 3/2, x= 6.43km

Ex

Walking at 4 / 5 of its normal speed, a school bus is 10 minutes late. Find its usual time to cover the journey.

A

 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 ?

A

 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 ((500-x)/70)-x/50 = 40/60, x= 188.9 kms 

Ex

A train travells at average speed of 100 km / hr, it stops for 3 mins after travelling 75 kms of diatance. How long it takes to reach 600 kms from the starting point ?

A

 Time taken to travel 600 kms= 600 / 100 = 6 hrs But it stop after travelling 75 kms , so number of stoping point in 600 kms will be= 600 / 75 = 8, but the last stoping point is actual end stoping so Number of stoping point will be 7, and time taken= 7*3= 21 minutes So total time = 6 hrs 21 mins