A and B start at the same timefrom L and M to go to M and L, a distance of 42 km at the rates of 4 kmph and 3 kmph respectively.They meet at N, then go to M and L and returned immediately and meet again at D. find the distance DN?

• 12 Km.
  
  First they will meet at N in 42/(4+3)= 6 hrs.
  In this 6 hrs, A covers 6*4=24 km from L and B covers 6*3=18 km from M.
  Now A will cover remaining 42-24=18 km in 18/4=4.5 hrs to reach at L but B will take (42-18)/3=8 hrs to reach at L. at the same time A will covers in his return journey from M a distance of (8-4.5)*4=14 km.
  So now B will start from L and A from 14 km from M and they will meet in (42-14)/7= 4 hrs at D.
  In this 4 hrs, B has covered 4*3= 12 km distance from L.
  So the distance of DN( calculated from L end)= 24-12= 12 km.
• 7 years agoHelpfull: Yes(3) No(0)
• ,total distance 84kms , 84/7 =12hrs, 4*12-3*12 =12kms
• 7 years agoHelpfull: Yes(0) No(0)