Question

partial credit, 7.2.40

A study found that the mean amount of time cars spent in​ drive-throughs of a certain​ fast-food restaurant was

139.9

seconds. Assuming​ drive-through times are normally distributed with a standard deviation of

31

​seconds, complete parts​ (a) through​ (d) below.

Click here to view the standard normal distribution table (page 1).

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Click here to view the standard normal distribution table (page 2).

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​(a) What is the probability that a randomly selected car will get through the​ restaurant's drive-through in less than

88

​seconds?

The probability that a randomly selected car will get through the​ restaurant's drive-through in less than

88

seconds is

0.0470

.

​(Round to four decimal places as​ needed.)

​(b) What is the probability that a randomly selected car will spend more than

190

seconds in the​ restaurant's drive-through?

The probability that a randomly selected car will spend more than

190

seconds in the​ restaurant's drive-through is

0.0530

.

​(Round to four decimal places as​ needed.)

​(c) What proportion of cars spend between

2

and

3

minutes in the​ restaurant's drive-through?

The proportion of cars that spend between

2

and

3

minutes in the​ restaurant's drive-through is

nothing

.

Answer 1