Aptitude Day 291

Answers of Day 290: 1. 950 m. 

                                    2. 350 m.

Problems on Trains:

1. A train moves past a telegraph post and a bridge 300 m long in 10 seconds and 25 seconds respectively. What’s the speed of the train?

Solution:

                  Let the distance and speed be x and y respectively.

                  Time = x/y = 10.

                   y = x/10

                  Speed = Length / time

                  x/10 = (x+300)/ 25

                  x = 200 m.

                  The speed of the train = 200/10

                                                      = 20 m/s

                                                      = 20*18/5 

                                                      = 72 km/hr.

          

2. How many seconds will a 200 m long train take to cross a man walking with a speed of 2 km/hr in the direction of the moving train if the speed of the train is 42 km/hr?

Solution:

                  Relative speed = 42-2 = 40 km/hr 

                                                      = 40*5/18 

                                                      = 100/9 m/s.

                  Time = 200*9/100 

                           = 18 seconds.