two men together start a journey in the same direction.they travel 9 kmph and 15 kmph respectively.after travelling for 6 hours the man travelling at 9kmph doubles his speed and both of them finish the distance in the same time.how many hours will they take to reach their destination?

• initially, A's-> 9 * 6 = 54 km , B's-> 15 * 6 = 90 km (At 6 hours)
  difference between them is 36 km's, A's speed is doubled (9 -> 18)
  no difference between A and B is 3 kmph so, 36 / 3 = 12
  initially 6 hrs +12 hrs = 18 hrs
  
  
• 11 years agoHelpfull: Yes(35) No(1)
• 18 hour is ans.....
  let total dis is=x
  thn acc to qus (x-54)/18=(x-90)/15
• 11 years agoHelpfull: Yes(7) No(5)
• initially A's speed= 9 kmph , B's speed=15kmph
  as they both are travelling in the same direction relative speed= 15-9=6kmph.
  we know that s=d/t,
  d=s*t -> d= 6*6 (time= 6 hrs given)-> d=36km (this is the distance travelled by both persons in 6 hrs)
  after 6 hrs A doubles his speed i.e 9*2 (18km).
  so A's speed=18 B's speed=15
  relative speed= 18-15 = 3km
  t=d/s -> t=36/3 -> t=12 hrs
  therefore total time taken= 6(initial time)+ 12
  = 6+12 -> 18hrs.
  
• 11 years agoHelpfull: Yes(6) No(0)
• relative speed of both men=6kmph so distance covered in 6 hrs=36 km.
  now, ist man doubles his speed that is 18 kmph. so time=36/18=2 hrs. total=8 hrs.
• 11 years agoHelpfull: Yes(3) No(12)
• as the time is same so we equate the time.
  asuming total dist to be x.
  now dist covered by A n B respestvly in 6 hrs is 54km & 90km.
  so the remaining dist for A and B are (x-54)&(x-90).
  equatin time we get (x-54)/(2*9)=(x-90)/15
  solving we get x= 270km..so time =270/15=18 min
• 11 years agoHelpfull: Yes(3) No(3)
• 9y+18z=15x,
  so y+z=x
  by solving above equations we got x/z=3/2
  by substuting in second y=1
  so 9+2(18)=3(15)
  so total 3 hours....
• 11 years agoHelpfull: Yes(2) No(9)
• ans is 18 hour i.e 270 km
  
• 11 years agoHelpfull: Yes(1) No(4)
• Initially there are two speed in the same direction so sp1 - sp2
  (15-9) =6km/hr.
  Speed =distance /time
  6=D/6
  D=36 km.
  Now after 6 hours the speed increases double i. e 18km/hr so
  Speed in the same direction i. e, total speed=18-15=3 km/hr.
  Time=distance/speed
  T=36/3
  12hours
  Total time=12hrs+6 hours
  18 hours Ans.
• 6 years agoHelpfull: Yes(1) No(1)