CaseStar field guide · Red Rock mini-cases
Red Rock mini-cases: six worked examples
After the study, Red Rock gives you 6 short, standalone cases at about 2 minutes each. They are the quickest marks in the game and the ones candidates most often run out of time for. Try each case below against a two-minute timer before opening the working.
How do the Red Rock mini-cases work?
Each case is a self-contained screen: a short paragraph, sometimes a small table or chart, and one or two questions. Candidates describe multiple-choice and numeric answers, a calculator that stays available, a research journal that resets between cases, and completed cases that lock once you move on. The themes often echo the study, but the data never carries over.
The question types repeat across candidate reports: a percentage or growth calculation, a weighted average, a simple probability or expected value, a ratio comparison, the right chart for a message, and a judgement about what a table does or does not prove. The six examples below cover each type once.
How do you solve a Red Rock mini-case in two minutes?
- Read the question before the text (10 s). Know what you are looking for.
- Find the two or three numbers it needs (30 s). Ignore the rest.
- Write the formula in words, then calculate (60 s).
- Sanity-check against the options and move on (20 s). If you are stuck at 2:30, pick your best estimate.
Six worked Red Rock mini-case examples
Case 1 · Growth
Visitor numbers at the ranger station
The ranger station logged 12,000 visitors in 2023 and 13,800 in 2024. By what percentage did visitors increase? A) 12.00% · B) 15.00% · C) 1,800 · D) 13.04%
Show the working
2023 → 2024: (13,800 − 12,000) ÷ 12,000 = 15.00%, so answer B. Option D (13.04%) divides by the 2024 value; option C (1,800) is the absolute change, not a rate.
Case 2 · Weighted average
Average ticket price across two seasons
In the low season 8,000 visitors paid €12 each; in the high season 2,000 visitors paid €20. What was the average price per visitor over the year?
Show the working
Revenue: 8,000 × €12 + 2,000 × €20 = €96,000 + €40,000 = €136,000. Visitors: 10,000. Average = €13.60. The simple average of the two prices, €16.00, ignores that four times as many visitors came in the low season.
Case 3 · Probability
Weather and the boat crossing
The ferry sails only when the wind is calm (80% of days) and the harbour is not closed for maintenance (90% of days). The two are independent. On what share of days does it sail, and how many crossings should the island expect in a 30-day month?
Show the working
The crossing runs only if both conditions hold. Assuming independence: 0.80 × 0.90 = 72.00%. Expected crossings in a 30-day month: 30 × 0.72 = 21.6, so about 22.
Case 4 · Ratio comparison
Which programme is most cost-effective?
| Programme | Budget | Birds fledged |
|---|---|---|
| A | €60,000 | 150 |
| B | €90,000 | 250 |
| C | €45,000 | 100 |
Which programme produced the most fledged birds per euro?
Show the working
Cost per bird fledged: A = 60,000 ÷ 150 = €400; B = 90,000 ÷ 250 = €360; C = 45,000 ÷ 100 = €450. Programme B is the cheapest per bird, even though it has the largest budget.
The trap is picking C for the smallest budget or B for the most birds without dividing.
Case 5 · Chart choice
Presenting a budget bridge
The conservation budget went from €500,000 to €430,000: staff costs rose by €40,000, equipment fell by €60,000 and grants fell by €50,000. Which chart best shows how the budget moved from the old total to the new one? A) Pie · B) Line · C) Waterfall · D) Clustered bar
Show the working
Waterfall chart. The message is how a starting total became an ending total through a series of increases and decreases. A waterfall shows each step’s contribution and the running total. A pie cannot show negatives, a line implies time, and a plain bar chart loses the bridge.
Case 6 · Data judgement
What does the table prove?
Seal sightings: 240 in 2023 over 80 survey-hours; 300 in 2024 over 120 survey-hours. Which statement is supported? 1) The seal population grew by 25%. 2) Sightings per survey-hour fell. 3) Extra survey-hours caused more seals to appear.
Show the working
Only statement 2 is supported. Sightings per survey-hour fell from 3.0 (240 ÷ 80) to 2.5 (300 ÷ 120). Statement 1 compares raw counts across different effort levels; statement 3 is a causal claim the table cannot show.
After practising.
Time yourself honestly. If a case took more than two and a half minutes, note which step was slow: finding the numbers, choosing the formula or doing the arithmetic. Each has a different fix, covered in the Red Rock math guide.
The McKinsey Red Rock simulator runs six new mini-cases after every full study, on the shared 35-minute clock, and reviews each answer afterwards. For the study itself, read the Red Rock Study guide.
Common questions
How many mini-cases are in Red Rock?
Candidates report 6 standalone mini-cases after the study, on the same 35-minute clock. Older reports mention a longer case section; the six-case format is what 2025–2026 candidates describe.
Do the mini-cases use the study data?
No. Each case brings its own short text or exhibit. They often share the study’s theme, which tempts candidates to look back at the study, but its numbers do not apply.
How long should each mini-case take?
About two minutes. Protect roughly twelve minutes for all six: candidates who spend longer in the study regularly report never reaching cases 5 and 6.
Are the mini-cases multiple choice?
Candidates describe a mix of multiple-choice and numeric-entry answers, with the calculator available. Some questions have two parts.
Are these the real McKinsey mini-cases?
No. The six cases on this page were written by CaseStar to teach the question types candidates report. They are not leaked or reconstructed assessment items.
Sources and limits
- McKinsey: Solve assessment overview and integrity rules
- McKinsey: Solve FAQ (August 2025)
- PrepLounge: “Didn’t perform well in Red Rock, did well in Sea Wolf”
- PrepLounge: McKinsey Solve, June 2026, Paris
- PrepLounge: Advice for McKinsey Solve
- PrepLounge: Advice to succeed on Redrock
- CaseStar: what changed in McKinsey Solve in 2026 (dated change log with confidence labels)
CaseStar (casestar.io) is an independent practice platform for consulting recruiting: timed McKinsey Solve simulators, including Red Rock, and voice case interviews. It is not affiliated with McKinsey & Company.
McKinsey publishes only a broad description of Solve. Details labelled as candidate-reported come from debriefs and can differ between candidates, regions and test versions. Worked examples on this page are original CaseStar exercises, not assessment questions. Your invitation and recruiter take precedence.