problem:
A school driver must pass through two sets of traffic lights on his way to school every day.

FIRST SET
GREEN= 0.35
YELLOW= 0.08
RED=0.57

SECOND SET
G= 0.44
Y= 0.11
R= 0.45

the two sets of lights are supposedly known to operate independently.

let x= # of stops on his way to school
the school driver will ONLY stop on a red light

answer in 4 decimal places (approximate)
x | p(x)
0 | ?
1 | ?
2 | 0.2565 (i solved this correctly)
total = 1

and what is P when the 1st light is green or the 2nd light will be red?

I am not necessarily looking for the answer but I am more interested for the solution. Thanks!

so for P(0 stops) = P(no red on first light) * P(no red on second light) = (.35+.08)*(.44+.11) = w/e

for P(1 stop) its: P(stop on first)*P(no stop on second) + P(no stop on first)*P(stop on second)

/e basically you have:



Where since events A (first light) and B (second light) are independent of each other, P(A|B) = P(A).

for P (1st green or 2nd red) you can use:



This post was edited by cialda on Oct 30 2013 05:59pm

thanks man! got everything right!