CDS Model Paper 4 Mathematics

Let the distance between X and Y be x‌km. Then, the
speed of A is

x

4

‌km∕h and that of B is

2x

7

‌km∕h. Relative speeds of the trains
=(

x

4

+

2x

7

)=

15x

28

‌km∕h
Therefore the distance between the trains at 7 a.m.
=x−

x

2

=

x

2

‌km
Hence, time taken to cross each other
=

x 2

15x 28

hr=

x

2

×

28

15x

hr=

14

15

×60‌min=56‌min
Thus, both of them meet at 7.56 a.m.