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Where a bread line in Cairo loses its minutes

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 bread line at a bakery in Cairo, Egypt is planned to run 600 minutes a day. At full speed it bakes 2 trays a minute (0.5 minutes a tray). Yesterday it stopped for 60 minutes (a breakdown and a change of recipe), baked 900 trays, and threw away 60 burnt or broken trays. What is its OEE, and where do the minutes go? (Fictional bakery, illustrative figures.)

2. Answers to clarifying questions

This case has no scripted clarifying answers. Answer from the prompt, and say "assume what you think is reasonable" if the prompt does not cover it.

3. 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.

OEE = good minutes / planned minutes
- Stops: planned minutes minus running minutes
- Key: Slow running: running minutes minus the minutes the trays should have taken
- Defects: minutes spent on trays that were thrown away

Exhibit 1

Reveal to candidate: when they ask for this data, say "Open Exhibit 1" (they press "Show exhibit 1" on their screen).

From planned minutes to good minutes on the bread line(minutes)

So-what

Slow running, not breakdowns, is the biggest loss: 90 of the 180 lost minutes.

4. 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: Running minutes
What a strong candidate does: Planned 600 minus 60 minutes of stops.
Running minutes: 600 - 60 = 540
Step 2: Minutes the trays should take
What a strong candidate does: 900 trays at the ideal 0.5 minutes each.
Ideal minutes for 900 trays: 900 × 0.5 = 450
Step 3: Slow running
What a strong candidate does: The line ran 540 minutes but did only 450 minutes of full-speed work.
Minutes lost to slow running: 540 - 900 × 0.5 = 90
Step 4: Defects
What a strong candidate does: 60 thrown-away trays used 0.5 minutes each.
Minutes lost to defects: 60 × 0.5 = 30
Step 5: Good minutes
What a strong candidate does: 840 good trays at 0.5 minutes each.
Good minutes: (900 - 60) × 0.5 = 420
Step 6: OEE
What a strong candidate does: Good minutes divided by planned minutes.
OEE (fraction): 420 ÷ 600 = 0.7
Step 7: The same answer from the three rates
What a strong candidate does: Availability 540/600, performance 450/540, quality 840/900, multiplied together.
OEE from the three rates (fraction): (540 ÷ 600) × (450 ÷ 540) × (840 ÷ 900) = 0.7

The recommendation to listen for

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

OEE is 70 percent: of 600 planned minutes, only 420 made good bread. Start with slow running, which loses 90 minutes, more than stops (60) or defects (30). Find out why the line runs below 2 trays a minute: dough not ready, an oven set cooler to avoid burning, or staff short at the start of the shift. Then cut the recipe change time. Every minute won back here is extra bread with no new oven.

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.