There are 2 toy cars facing each other at a distance of 500 cm from each other. Each car moves forward by 100 cm at a speed of 50 cm/s and then moves backward by 50 cm at a speed of 25 cm/s. How long will it take for the cars to collide?

a) 12s b) 14s c) 16s d) 13s

• Ans : b)14s
  
  a toy car moves forward 50 cm in 4 seconds((100/50)+(50/25))=4.
  
  now each car has to move 500/2=250 cm.
  after last 100 cm the two car collide so no going back.
  so each car will move 150 cm having a speed of 50cm in 4 sec.
  so it takes 150/50*4=12 sec.the two cars move 100 cm forward within 2sec.
  so 12+2=14
• 12 years agoHelpfull: Yes(25) No(2)
• ANS IS 16 S BCZ IN MOVING FORTH AN D BACK IT TAKES 4 SEC AND COVERS 100 CM AND DISTANCE IS 500 SO TIME WILL BE 16 SEC
• 9 years agoHelpfull: Yes(2) No(1)
• Each car moves a 100 cm forward and 50 cms backwards
  the total forward and a backward moment is defined as a cycle.
  each cycle takes 4 seconds as 2 seconds 100 cms forward at 50 cm/s and backwards at 25 cm/s
  in each cycle of 4 seconds each car moves 50 cms forwards and distance betweeen car is reduced by 100 cms
  cycle 1 4 seconds
  Car A moves 50 cms and same the car B
  now the distance is 400 cms
  cycle 2 8 seconds
  Car A moves 100 cms and same the car B
  now the distance is 300 cms
  cycle 3 12 seconds
  Car A moves 150 cms and same the car B
  now the distance is 200 cms
  now in the last cycle the collision occurs
  as each car moves 100 cms in 2 seconds
  so the 200 cms is covered by both cars
  so after an instant collision, at the 12+2= 14 seconds
  the car moves backwards
  hence the answer is 14 seconds
  credits to:
  raghavan iyengar
  hcl technologies
• 7 years agoHelpfull: Yes(2) No(0)