Mathematics 9709 · AS & A Level · Discrete random variables
Discrete random variables — practice question
At a particular road junction from Bromley, vehicles must turn left, right or continue straight ahead. It is known over time that 30% turn left, 25% turn right and 45% continue straight ahead. The driver of every vehicle makes the choice independently of every other driver.
(a)[2]
Find the probability that the next three vehicles approaching this junction from Bromley all travel in different directions.
(b)[2]
Find the probability that, among the vehicles approaching this junction from Bromley today, the first vehicle to turn left is before the 9th vehicle.
(c)[2]
Find the probability that, among the vehicles approaching this junction from Bromley today, the 2nd vehicle to turn left is the 7th vehicle.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correct probability calculation, for example $0.3\times0.25\times0.45\times6$ or an equivalent expression.” …