Interviewer view · keep this screen to yourself

Cutting a theme-park queue

You run the case. Read the prompt, answer questions from the notes below, and share data only when the candidate asks for it or gets stuck. Score at the end.

Case timer

00:00

Target length:

1. Read the prompt aloud

Read it slowly, then pause. Let the candidate ask questions before they structure.

A popular ride at a theme park in Abu Dhabi serves 1,200 people an hour, and at peak the queue holds about 2,400 people. The chart below shows the queue through the day. Roughly how long is the wait, and how would you reason about cutting it?

The prompt refers to Exhibit 1. After reading it, say: "Open Exhibit 1 now."

Format note: Interviewer-led: the interviewer shows the queue chart and asks for the peak wait, then for levers, then for which lever to test first.

2. Answers to clarifying questions

Give these answers only if the candidate asks. If they ask something not listed, give a sensible answer or say it does not matter here.

If asked: What is the goal: shorter waits, more riders, or happier guests?
Answer: Happier guests; waits over an hour hurt the park's ratings.
If asked: Is the ride running at full capacity?
Answer: Mostly, but it stops about 10 percent of the time for safety checks.

3. The hypothesis a strong candidate states

Listen for an early, testable guess like this one. It does not need to match word for word.

The wait depends on how many people are ahead and how fast they are served. My hypothesis is that the fastest improvement comes from spreading peak demand, since building capacity is slow and costly.

4. A model structure

Compare the candidate's structure with this one. A different split can be just as good if it is clean and fits the problem.

Wait = queue length / service rateThis comes from wait = queue length / service rate: serve faster, spread arrivals, or change how the wait feels.
- Serve faster: less downtime, faster loading, more seats
- Key: Spread arrivals: timed return tickets, off-peak incentives
- Change how the wait feels: shade, entertainment, accurate signs

Exhibit 1

The prompt uses this exhibit, so the candidate opens it right after you read the prompt ("Show exhibit 1" on their screen).

Queue length at the ride through the day (people)(people in the queue)

So-what

The queue is four times longer at midday than in the early evening, so there is quiet capacity later in the day to move guests into.

5. The working, step by step

Each step shows how a strong candidate works it out. Share a new fact from it only when the candidate asks or is stuck, and let them do the math: the result in the dark box is what they should reach.

Step 1: Estimate the wait
What a strong candidate does: 2,400 people in line and 1,200 served an hour.
Wait (hours): 2,400 ÷ 1,200 = 2
Step 2: Lever 1: remove downtime
What a strong candidate does: If the ride stopped for checks outside peak hours instead, it would serve 1,200 / 0.9 people an hour at peak, and the wait would fall only a little.
Wait without downtime (hours): 2,400 ÷ (1,200 ÷ 0.9) = 1.8
Step 3: Lever 2: timed return tickets
What a strong candidate does: If half the peak queue takes a timed return ticket instead of standing in line, 1,200 people remain, provided return slots are set in quieter hours; otherwise returners take capacity from the standby line.
Wait with timed tickets (hours): 1,200 ÷ 1,200 = 1
Step 4: Where the quiet hours are
What a strong candidate does: Read the chart: at 18:00 only 600 people are queuing, a wait of about 30 minutes, so return slots belong in the late afternoon and evening.
Wait at 18:00 (minutes): 600 ÷ 1,200 × 60 = 30

The recommendation to listen for

At the end, say: "The CEO walks in. What is your recommendation?"

Pilot timed return tickets first, and move safety checks out of peak hours in parallel. First, the wait is about two hours, and removing downtime alone cuts it only to about 1.8 hours. Second, timed tickets for half the peak queue cut the physical wait to about one hour at low cost, provided return slots are set in quieter hours; otherwise returners take capacity from the standby line. Third, the chart shows those quieter hours exist: by 18:00 the queue is only 600 people, a wait of about 30 minutes. Beyond these two structural levers, a third changes how the wait feels: shade, entertainment, and accurate wait-time signs.

Risks a strong answer names: Guests may dislike booking return times; Timed tickets can move the crowd to other rides.

Next steps: Pilot timed tickets on this ride for two weekends; Measure guest ratings before and after.

Strong versus weak

A strong answer

Built a simple model from scratch, used it to find and size the levers, and picked a cheap pilot first.

A weak answer

Listed random ideas (music, an app, more staff) with no model and no sense of which would help most.

Score the candidate

Score each criterion from 1 to 5. A 2 or a 4 sits between the descriptions.

Structuring

1: No clear structure, or a memorized framework that does not fit the problem.
3: A sensible structure, but with some overlap, a gap, or no clear priority.
5: A structure built for this problem, with no overlap and no gaps, a stated hypothesis, and a clear first step.

Math

1: Frequent errors, no units, or needed heavy help to finish.
3: Right answers but slow or messy working, or one error caught late.
5: Accurate and clearly narrated, with units, a sense check, and what the number means.

Exhibit reading

1: Read the chart aloud without finding the number that matters.
3: Found the key number but gave only part of the so-what.
5: Pulled the right number quickly and said what it means for the case.

Synthesis

1: Summarized what was done, with no clear answer.
3: Gave an answer, but with weak reasons or no next step.
5: Answer first, then two or three reasons with numbers, the main risk, and next steps.

Communication

1: Hard to follow: long silences, no signposting.
3: Clear most of the time, with some rambling.
5: Calm and concise, signposted each step, and checked in with the interviewer.

Total

0 out of 25

Score all five criteria to see the band and the feedback template.