Car A leaves city C at 5 pm and drives at a speed of 40 kmph. 2 hours later another car B leaves city C and drives in the same direction as car A. In how much time will car B be 9 km ahead of car A. Speed of car B is 60 kmph.
option
a) 4.25 hrs
b) 4.17 hrs
c) 4.30 hrs
d) 4.45 hrs

• first we will calculate the distance travel by car A in two hours i.e. 80 km. now their relative speed is 20 kmph and distance will be 89 km. so car B will be ahead of car A in (89/20) = 4.45 hrs. ans is d.
• 11 years agoHelpfull: Yes(47) No(2)
• we take the relative speeds of the 2 cars.
  relative speed=(60-40)=20km/h
  the car a has travelled (40*2)km in 2 hrs.
  thence car b has to travel 80km+9km ahead to get ahead by 9 km.
  so time= 89/20=4hr 45 min.
• 11 years agoHelpfull: Yes(17) No(2)
• car A started 2 hours before ,so distance covered by car A when Car B starts is:
  40*2=80 km(dis= speed*time)
  now make a equation using distance(equating both distance ):
  car A cover 80 km and going in 40 kmph, car B is starting with 60 kmph-
  80+y*40=y*60, y is the time taken by the cars(distance covered by cars are equal)
  please, understand that both cars are travelling ,but car B have to go 9 km apart, so equating time relation of both cars will help:
  w/40=(w+9)/60
  w=18 km (after travelling 18 km by car A , car b will be 9 km ahead)
  now cal the time
  speed*time=distance
  40*t=18
  t=.45*60(convert into mins)
  t=27
  so the answer is 4 hr,27mins
  solutions also can be derived using relative speed
• 11 years agoHelpfull: Yes(16) No(5)
• After 4 hrs, B and A make the same distance. B to be 9km ahead of A, (ie.9km in 20km diff)..it wil take .45 hrs.. so in total For B it wil take 4.45 hrs
• 11 years agoHelpfull: Yes(10) No(1)
• intialy carA=0 carA=80km
  after 1hr 60 120
  2hr 120 160
  3hr 180 200
  4hr 240 240
  4.5 260 - 270 =10
  30min=10km
  ??=9km
  27min
  4hr 27min
  option a
• 11 years agoHelpfull: Yes(7) No(0)
• relative speed of 2 cars =(60-40)=20km/h
  the car a has travelled (40*2)km =80km in 2 hrs.
  so car b has to travel 80km+9km to get ahead by 9 km.
  so time= 89/20= 4.45hr
  
  
• 11 years agoHelpfull: Yes(6) No(2)
• (c)4.30hrs
  4hrs it takes to just meet it
  then approx 27 min to reach 9km ahead of it
  
• 11 years agoHelpfull: Yes(4) No(0)
• 4 HOUR 27 MINUTES WILL BE THE ANSWER
  
• 11 years agoHelpfull: Yes(3) No(2)
• The ans should lie b/w 4.25 to 4.30 as in 4 hrs they jst meet so in 4.30 hrs B will be 10km ahead of A.so 4.30hrs should be the ans.
• 11 years agoHelpfull: Yes(1) No(1)
• if A travel at a speed of 40kmph .at the time of 11.30 it travelled the 260 km.as well B at a speed of 60 kmph.at the time of 11.29 travelled 269.so it 9km ahead of A(surely).because in 4 hours B was (4 x 60)=240 km,then 20 min=20 km +9 min=9 km finally,(4+20+9)=4:29 hours in option 4:30 hours
• 10 years agoHelpfull: Yes(1) No(0)
• speed of 2 car in speed=60-40=20km/hr
  car travel 40*2=80km in 2 hr
  b has travel 80km+9km=89km
  89/20=4.45
• 10 years agoHelpfull: Yes(0) No(3)
• Relative speed = 60 - 40 = 20 kmph
  Initial gap as car B leaves after 2 hours = 40 x 2 = 80 kms
  Car B should be 9 km ahead of the A at a required time so it must be 89 km away
  Time = 89 / 20 = 4.45 hrs or 267 mins
• 5 years agoHelpfull: Yes(0) No(0)
• relative speed=(60-40)=20km/h
  the car Atravelled (40*2 = 80)km in 2 hrs.
  thence car b has to travel 80km+9km ahead to get ahead by 9 km.
  so time= 89/20=4hr + 27min. (267-240 =27)
  ANS = 4hrs 27min
• 4 years agoHelpfull: Yes(0) No(0)
• speed of A = 40 kmph, speed of B = 60 kmph
  distance traveled by A in 2 hours..
  d = s*t = 40 * 2 = 80 km
  distance B must travel to be 9 km ahead of A = 80 km + 9 km = 89 km
  Relative speed of A and B = 60 - 40 = 20 kmph
  time taken by B to be 9 km ahead of A : t = d/s = 89km/20kmph = 4.45 hours
• 2 years agoHelpfull: Yes(0) No(0)