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2 Answers

Best answer
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Here the trick is :

Let us consider a distance frame in which we have a bus followed by a gap after bus followed by car followed by a gap after car..

So the distance in this frame  =  20 + 10 + 15 + 5

                                            =  50 m

Now given speed                   =  36 km / hr

                                            =  36 * 5 / 18 m/s

                                            =  10 m/s

Hence time taken to cover 50 m   =   50 / 10

                                                 =   5 s

In other words , one bus and one car is involved in this time frame

Hence in 5s , no of vehicles passed  =  2

          in 1s , no of vehicles passed  =  2/5

   ==> in 1 hr i.e. in 3600 s , no of vehicles passed    =    2/5  *  3600

                                                                              =    1440

Hence the correct answer should be 1440..Hence option A)

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Another easy method:

Since they are travelling with constant speed 36 kmph therefore in one hour they will travel only 36 km

Total distance covered(size of car and truck + gap) =  20+15+10+5 = 50 mt

No. of slots of 50 mt in 36 km = 36000/50 = 720

In each slot 2 vehicle is there, so in 720 slot = 720 *2 =1440

 

Answer:

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