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Two cars A and B start together in the same direction from the same place . The first goes with uniform speed of 40km/hr . The second goes at a speed of 36km/hr in the first hour and increases the speed by 1km/hr each succeeding hour . After how many hours will the second car overtake the first car if both car go non-stop ?

 Jul 8, 2020
 #1
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Let's look at the differences in speed each hour.....

hour

1      2    3   4   5    6    7   8    9    10

diff

-4    -3   -2  -1  0     1   2   3    4      5

 

so at hour 5 they are the same speed....then the originally slower train starts gaining so that at hour 9 it has made up the miles it lost in the first 4 hours of going slower

 

at hour 9 they should be at the same point

 

check:   9 hr (40 km/hr) = 360 km        

                          other train  36  + 37 +38 +39 +40 +41 +42 + 43 + 44  = 360 km

 Jul 8, 2020

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