Thursday, 18 February 2016

Shortcut of the day:Qunatitative Aptitude


                                              SHORTCUT OF THE DAY
If a train crosses  L1  m and  L2  m long brings or platform or tunnel in T1  seconds and  T2 seconds respectively , then the length of the train is { (L1 T2 –L2T1)/(T1-T2)}meters  and the speed of the train is [(L1-L2)/(T1-T2)]  m/sec.

Ex:  A  train crosses 210 metres 122 metres long  bridge in 25 seconds and 17 seconds respectively . Find the length and speed of the train.
Sol:     Applying the above theorem, we have the length of the train                                                                                                       
                                (210*17-122*25)/(25-17)= 520/8= 65 m

              And  speed of the train  
                               (210-122)/(25-17)=88/8=11 m/s