Question

A person goes to work across three intersections. The probability of seeing the red light at the first intersection is 60%, the probability of seeing the red light at the second intersection is 70%, and the third intersection is 80%. Calculate the probability of the person walking without a red light

Answer 1

1. add together all (3) percentages                                                                        60+70+80=210
2. subtract the answer from 300 (300 because there were 3 percentages)   300-210=90
3. divide this answer by 3 (also because there were 3 percentages)            90/3=30
4. the probability of the person walking without a red light is 30%