Customers arrive at the local grocery store at a steady rate of 40 an hour. Thirty percent of these customers purchase 10 items or less and go to the express line where they enjoy an average checkout time of 5 minutes. Customers that don't meet the express line criterion go to checkout line #2 where they spend an average of 10 minutes checking out. How many people are checking out in both lines on average?
A) less than or equal to 1.0
B) greater than 1.0 but less than or equal to 3.0
C) greater than 3.0 but less than or equal to 5.0
D) greater than 5.0

Question

Quizplus · Accepted Answer

The average number of people checking out in both lines can be calculated by first determining the number of people using each line per hour and then converting that into the number of people checking out per minute. For the express line, 30% of 40 customers, which is 12 customers, use it per hour. Since their checkout time is 5 minutes, this translates to 12 customers / 60 minutes * 5 minutes = 1 customer at any given time. For checkout line #2, 70% of 40 customers, which is 28 customers, use it per hour. With a checkout time of 10 minutes, this translates to 28 customers / 60 minutes * 10 minutes = 4.67 customers at any given time. Adding both gives 1 + 4.67 = 5.67 customers checking out on average at any given time, which is greater than 5.0.

Customers Arrive at the Local Grocery Store at a Steady