Detailed description
Tree diagrams showing probabilities of green or red.
Probability of the first light being green is 0.3 and probability of the first light being red is 0.7. Probability of green and then green is equal to 0.3 × 0.6 = 0.18. Probability of green and then red is equal to 0.3 × 0.4 = 0.12. Probability of red and then green is equal to 0.7 × 0.4 = 0.28. Probability of red and then red is equal to 0.7 × 0.6 = 0.42.
