math
posted by Anonymous .
A traffic light follows the pattern green, yellow, red for 55, 5, and 20 seconds, respectively. What is the probability that the driver approaching this light will find it green or yellow?

Total = 55 + 5 + 20 = 80
P( green) + P( yellow)  P(green and yellow)
( 55 + 5)/80 0
P = 60/80 = .75