Answer:
a) 91.33% probability that at most 6 will come to a complete stop
b) 10.91% probability that exactly 6 will come to a complete stop.
c) 19.58% probability that at least 6 will come to a complete stop
d) 4 of the next 20 drivers do you expect to come to a complete stop
Step-by-step explanation:
For each driver, there are only two possible outcomes. Either they will come to a complete stop, or they will not. The probability of a driver coming to a complete stop is independent of other drivers. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which 
is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
20% of all drivers come to a complete stop at an intersection having flashing red lights in all directions when no other cars are visible.
This means that 
20 drivers
This means that 
a. at most 6 will come to a complete stop?
In which
91.33% probability that at most 6 will come to a complete stop
b. Exactly 6 will come to a complete stop?
10.91% probability that exactly 6 will come to a complete stop.
c. At least 6 will come to a complete stop?
Either less than 6 will come to a complete stop, or at least 6 will. The sum of the probabilities of these events is decimal 1. So
We want 
. So
In which
19.58% probability that at least 6 will come to a complete stop
d. How many of the next 20 drivers do you expect to come to a complete stop?
The expected value of the binomial distribution is
4 of the next 20 drivers do you expect to come to a complete stop
