A and B start simultaneously from P and Q towards Q and P respectively.The speeds of A and B are 25kmph and 32kmph resp.They meet at R and immediately return to their respective starting positions after exchanging their speeds.If PQ=2000km,then the difference in times taken by A and B t reach their respective starting positions is??(Please post your approach,m getting 20 as answer )

1) 15.5 hrs
2) 20 hrs
3) 16hrs
4) 17.5hrs

• we can solve this question using the conventional method by assuming the distances to be X and (2000-X).
  but an easier and faster method would be
  if we consider A , who is travelling at 25 km/h from P till R then B is travelling the rest from Q to R at 25 km/h and
  similarly B is travelling at 32 km/h frm Q till R then A is travelling the rest from R to P at 25 km/h
  so basically the PQ distance is travelled once at 25 km/h by two different people A and B
  Also PQ distance is travelled once at 32 km/h by the same A and B
  
  so
  time , T1=Distance /Speed = 2000/25 = 80 hours
  time , T2 = 2000/32 =62.5 hours
  
  difference in time = T1 -T2 = 80 - 62.5 = 17.5 hours
  
  hope you understand :)
• 4 years agoHelpfull: Yes(1) No(0)