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Problem-Solving and Data Analysis / Probability and conditional probability Difficulty: Easy

	$1$ $1$ visit	$2$ $2$ or more visits	Total
Less than $40$ $40$ years old	$15$ $15$	$15$ $15$	$30$ $30$
At least $40$ $40$ years old	$20$ $20$	$85$ $85$	$105$ $105$
Total	$35$ $35$	$100$ $100$	$135$ $135$

The table summarizes customers who visited a car dealership in the last month by age and number of visits they made to the dealership. If a customer from the last month is selected at random, what is the probability that the selected customer is at least $40$ years old?

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Explanation

Choice D is correct. Based on the table, there are a total of $135$ customers who visited the car dealership in the last month, and $105$ of these customers are at least $40$ years old. If a customer from the last month is selected at random, the probability that the selected customer is at least $40$ years old is equal to the number of customers who are at least $40$ years old divided by the total number of customers. Therefore, the probability that the selected customer is at least $40$ years old is $StartFraction 105 Over 135 EndFraction$ .

Choice A is incorrect. This is the probability that the selected customer is less than $40$ years old.

Choice B is incorrect. This is the probability that the selected customer visited the dealership $1$ time in the last month.

Choice C is incorrect. This is the probability that the selected customer visited the dealership $2$ or more times in the last month.