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Interesting question about car driver

  • Thread starter Alexsandro
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  • #1
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Hello, I tried to model and answer this question, but I didn't get success. Could someone help me ?

Question:

A California driver decides that he must switch lanes every minute to get ahead. If he is on 4-lane divided highway and does this at random, what is the probability that he is back on his original lane after 4 minutes (assuming no collision) ? [HINT: the answer depends on whether he starts on an outside or inside lane.]
 

Answers and Replies

  • #2
AKG
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If the driver is outside at the far left , you have these possibilities

R,R,R,L
R,R,L,L
R,R,L,R
R,L,R,L
R,L,R,R

R IS MOVING RIGHT , L IS MOVING LEFT

He returns to his lane when the number of R equals the number of L

p= 2/5

When the driver on the second lane from left , we have these possibilities

L,R,L,R
L,R,R,L
L,R,R,R
R,L,L,R
R,L,R,L
R,L,R,R
R,R,L,R
R,R,L,L

WHEN #R=#L, He returns to his original position

p = 5/8
 
  • #4
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How reach the right answer ?

Mithal said:
If the driver is outside at the far left , you have these possibilities

R,R,R,L
R,R,L,L
R,R,L,R
R,L,R,L
R,L,R,R

R IS MOVING RIGHT , L IS MOVING LEFT

He returns to his lane when the number of R equals the number of L

p= 2/5

When the driver on the second lane from left , we have these possibilities

L,R,L,R
L,R,R,L
L,R,R,R
R,L,L,R
R,L,R,L
R,L,R,R
R,R,L,R
R,R,L,L

WHEN #R=#L, He returns to his original position

p = 5/8
------------------------------
This question is in a book, that giving the answers.

The right answers are:
from an outside lane: 3/8;
from an inside lane: 11/16.
 
Last edited:

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