Queueing Analysis for an Ice Cream Vending Machine

MathematicsQueueing TheoryMedium

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EXAMPLE 3: Ephebi operates an automatic ice cream vending machine at the PHC lounge. Customers arrive in a random fashion, approximated by the poisson distribution, at the rate of 45 per hour at peak demand period. The vending machine is programmed to serve customers at a constant rate of 0.8 minutes per customer. Determine: 1. The average number of customers in the queue 2. The average time spent by a customer at the vending shop.

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Step 1

Hi Merry, let's solve this queuing theory problem together. First, let's read the details and identify the parameters of our system.

Given Information

* Arrival process: Poisson with rate $\lambda = 45$ customers per hour

* Service time: Constant at $0.8$ minutes per customer

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Step 2

Because the service time is constant, this is an M D one queuing system, where D represents deterministic or constant service times.

Model: $M/D/1$ Queue

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Step 3

Let's first convert the units so that the arrival rate and service rate are in the same time unit. We will use hours.

Step 1: Calculate the Service Rate ($\mu$)

$$ \mu = \frac{1}{\text{Service Time}}$$
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Step 4

The service time is zero point eight minutes per customer. In hours, that is zero point eight divided by sixty.

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Step 5

Multiplying one point two five customers per minute by sixty minutes gives us seventy-five customers per hour.

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Step 6

Now, let's calculate the system utilization factor, rho, which is lambda divided by mu.

Step 2: System Utilization ($\rho$)

$$\rho = \frac{\lambda}{\mu}$$
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Step 7

Substituting forty-five for lambda and seventy-five for mu, we get zero point six.

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Step 8

Let's solve part one: the average number of customers in the queue, represented by L sub q.

Part (i): Average Number of Customers in Queue ($L_q$)

For an $M/D/1$ queue, the formula for $L_q$ is:

$$L_q = \frac{\rho^2}{2(1-\rho)}$$

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About This Question

Subject
Mathematics
Topic
Queueing Theory
Difficulty
Medium
Question Type
Open Ended

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