McKinsey Solve Redrock Island (Redrock Study): Format, Strategy, and a Worked Example (2026)

Redrock Island is the first game in McKinsey Solve. You get 35 minutes to work through one research study and six short cases, all built on data about an ecosystem. You may know it as Redrock Study, its earlier name. They are the same game.

McKinsey Solve now runs 95 minutes in total: Redrock Island for 35 minutes, Sea Wolf for 30, and Sustainable Futures Lab for 30. This guide covers how Redrock Island works, the math it needs, a method for each phase, and a full worked example from Prepmatter's simulation.

If you'd rather watch than read, here is Deniz, Prepmatter's founder, solving a complete Redrock Island scenario in our simulation:

What Is Redrock Island in McKinsey Solve?

Redrock Island is a data analysis game inside McKinsey Solve where you play a research assistant working through field data in the Redrock labs.

The game hands you a written brief and a set of exhibits about an ecosystem problem, such as a predator being reintroduced to a forest. You pull out the relevant numbers, answer quantitative questions with a built-in calculator, and complete a short report. Then you solve six independent mini cases.

McKinsey introduced the game in 2023 as Redrock Study. It runs first in the Solve sequence, before Sea Wolf and Sustainable Futures Lab, on its own 35-minute timer. Of the three games, it is the closest to a case interview: read, structure, calculate, conclude.

The game needs no business or biology knowledge. It tests how quickly you find the numbers that matter, how accurately you calculate, and how clearly you report the result.

How Does Redrock Island Work?

Redrock Island has two parts on one 35-minute timer: a study with three stages, and a set of six mini cases.

Two tools run through the whole study:

• The Research Journal. You drag data points from the brief and the exhibits into the journal to collect them. You can rename, reorder and highlight the entries. Your answers from the Analysis stage are added to it automatically.
• The calculator. It handles addition, subtraction, multiplication and division, and it keeps a history of your calculations. You can drag a result from the calculator straight into an answer field.

One rule shapes how you should work. From the Analysis stage you can still go back to the brief and the exhibits. Once you move on to the Report, you cannot. From that point, the journal is all you have.

The mini cases are separate from the study. Each one brings its own short text and its own chart or table, and nothing carries over from one case to the next.

Older versions of the game had up to 10 dense case questions. The current version has 6 mini cases, and they are shorter and more focused.

The Four Phases of Redrock Island

Each phase asks for a different skill: selecting, calculating, reporting, then switching quickly between small problems.

Phase 1: Investigation

You see three things: the objective of the study, a written brief, and one or more exhibits such as charts and tables. The brief mixes numbers you will need with background you will not. Your job is to drag the useful data points into the Research Journal.

Each entry in the journal carries a label and a description, so a number like 550,000 tells you what it is and which scenario and year it belongs to. Rename an entry when its label is not clear enough to find later.

Phase 2: Analysis

You answer three to four quantitative questions, most of them with sub-questions. The arithmetic is simple. The difficulty is in the layers: one answer feeds the next, and some questions need the same step repeated across several years.

You calculate in the built-in calculator and drag results into the answer fields. If a number is missing from your journal, you can still go back to the brief and the exhibits.

Phase 3: Report

The report has two parts.

• Written report. A pre-written summary of the study with blanks. You fill them by dragging entries from your journal, typing a value, or choosing from a drop-down menu.
• Visual report. You choose the chart type that best shows a given comparison, then enter the values.

Most of the blanks ask for numbers you already calculated in the Analysis stage, which is why a well-organized journal matters.

Phase 4: Mini Cases

You solve six short cases. Each gives you a few lines of context, usually with a chart or table, then asks one or two questions. The questions come in four types:

• Word problems: a short scenario with numbers and a calculation to make, such as a ratio or a change in percentage points
• Formula selection: a situation is described, and you choose the formula that fits it
• Verbal reasoning: you decide which statement is true based on the data
• Chart selection: you choose the chart type that best represents the data

The cases are easier than the study, but the clock is not. With about 15 minutes for six cases, you have two to three minutes each.

What Math Does Redrock Island Need?

Redrock Island needs fast, accurate arithmetic with percentages, not advanced math.

Two habits prevent most errors. Read whether a question asks for a percentage or for percentage points. And for multi-year questions, calculate one year at a time and write down each result, because every year starts from the last one.

Redrock Island Strategy: A Method for Each Phase

A good Redrock Island run front-loads the collecting, so the calculating and reporting go fast, and it protects 15 minutes for the cases.

Phase 1: Read the Objective, Then Collect What It Needs

Start with the objective. It tells you which numbers matter. In our example the objective is to analyze how reintroducing a predator affects the herbivore population and the vegetation cover. Everything about wolves, hares and vegetation is relevant from that moment.

Then collect:

• Every constant in the brief, such as a population size, a rate or a threshold
• Every relationship, such as "a 10% increase in plant cover adds 3,000 deer"
• The exhibit data, one scenario at a time, so the journal stays in order

Skip background sentences without numbers, and skip a number you already have.

Be selective, but not stingy. The game records what you collect, so dragging in every line is not a strategy. At the same time, you cannot return to the brief once you reach the Report. If a number relates to the objective and you are unsure, collect it.

Phase 2: Use the Calculator for Everything

Read a question and its sub-questions before you calculate, so you know what the chain leads to.

Do every calculation in the built-in calculator, even the ones you can do in your head. The calculator keeps a history, and McKinsey looks at how you work as well as what you answer. Break long calculations into steps. For a population over several years, calculate each year separately.

Before you use a journal entry, open its description. Two numbers can look alike and belong to different scenarios.

Phase 3: Let the Journal Do the Work

The written report mostly asks for numbers you already have. Your Analysis answers are in the journal, so find the right entry, confirm its scenario and year, and drag it in.

For the chart, match the type to the comparison:

• Bar chart: comparing categories, such as two scenarios side by side. Use a clustered bar chart when you compare two scenarios at two points in time.
• Line chart: a trend over time, such as a population from Year 0 to Year 5
• Pie chart: parts of a whole that add up to 100%

Phase 4: Question First, Then the Data

Read the question before the context. Most cases need one or two numbers from a chart, and the question tells you which.

Each question type has its own quick routine:

• Word problems: pull out the numbers, name the operation, calculate.
• Formula selection: decide what kind of relationship is described, such as growth, a ratio or a percentage, then match it to a formula.
• Verbal reasoning: remove the statements that are clearly wrong, then check the rest against the data one by one.
• Chart selection: apply the bar, line and pie rules from Phase 3.

Look for the shortcut before you calculate. If every option is divided by the same number, compare the numerators and skip the division. If a question adds a condition, such as a minimum survival rate, remove the options that fail it first.

If a case has taken three minutes, enter your best answer and move on. Six cases share the same 15 minutes.

Redrock Island Walkthrough: A Full Practice Scenario

The example below follows Deniz through Selva Nova, a scenario in Prepmatter's McKinsey Solve simulation. The scenario and its numbers are Prepmatter's. McKinsey's real test uses its own, but the stages and the types of question work the same way.

The Brief

Selva Nova is a forest that lost its apex predator, the Silver Wolf. Without wolves, the Mountain Hare population exploded and overgrazed the vegetation. The government plans to release 150 wolves and monitor the effect for five years.

The objective: analyze the impact of reintroducing a predator on Selva Nova's herbivore population and vegetation cover.

The data points Deniz collects from the brief:

• 150 wolves, and each wolf eats 500 hares a year
• 500,000 hares today, growing 10% a year
• While hares stay above 500,000, vegetation cover falls 3% a year
• 50,000 deer, and each 10% increase in plant cover adds 3,000 deer
• Each 5% change in vegetation cover changes tourism revenue by $25,000

He then collects the exhibit data scenario by scenario: the projected hare population with and without wolves, and the projected vegetation cover, which starts at 80% and reaches 100% by Year 5 with wolves.

In the video, Deniz plays it safe and collects every data point in the brief and both exhibits. A more selective pass, guided by the objective, is the better habit.

The Analysis Questions

How many hares will 150 wolves eat per year? 150 × 500 = 75,000.

After Year 5, in which year does the hare population first fall to 300,000 or below? The Year 5 population with wolves is 386,890. Each year it grows 10% and then loses 75,000 hares.

The answer is Year 8. This is the layered kind of question the game likes: no single step is hard, but you have to repeat it carefully.

What share of the Year 5 population must be relocated to reach 300,000 immediately? 386,890 − 300,000 = 86,890. Then 86,890 ÷ 386,890 = 22.46%.

By how many percentage points does vegetation cover increase with wolves? From 80% to 100%, so 20 percentage points.

How many deer will there be at the end of Year 5? A 20-point increase in cover is two steps of 10%, so 2 × 3,000 = 6,000 more deer. 50,000 + 6,000 = 56,000.

Without wolves, what is the vegetation cover in Year 5, and what is the loss in tourism revenue? Cover falls 3% a year for five years: 80% − 15% = 65%. A 15% loss is three steps of 5%, so 3 × $25,000 = $75,000.

The Report

The written report asks for numbers Deniz already has: the 10% growth rate, the fall in cover from 80% to 65%, the $75,000 loss, the 75,000 hares eaten per year, the Year 5 hare population, the 56,000 deer, and the $100,000 of additional tourism revenue in Year 5, which comes from the second exhibit.

That last number shows why he collected the exhibit data earlier. At this stage he can no longer open the exhibit.

For the chart, the task is to compare vegetation cover in Year 0 and Year 5, with and without wolves. He picks a clustered bar chart and enters 80 and 80 for Year 0, then 65 without wolves and 100 with wolves for Year 5.

Two of the Six Mini Cases

Which tree captures the most carbon per dollar? The case gives cost, carbon captured and survival rate for four species.

Eucalyptus wins on carbon per dollar. The follow-up adds a condition: only species with a survival rate of at least 80%. Eucalyptus survives at 75%, so it drops out, and Pine, the next best on carbon per dollar, is the answer. No new calculation is needed.

Which project introduces the most plant species per dollar? Three conservation projects share the same $12 million budget.

The last question asks for species per dollar. Every project spends the same $12 million, so the project with the most species also has the most species per dollar. The answer is Project A, without another division.

Five Redrock Island Mistakes to Avoid

The questions in Redrock Island are simple. The avoidable mistakes come from how the game is built.

1. Collecting too little in the Investigation. Once you reach the Report, the brief and the exhibits are gone. A number you left behind cannot be recovered.
2. Mixing up scenarios. A study usually compares two scenarios across several years. Using the "without" number where the "with" number belongs is the easiest way to lose a correct calculation.
3. Confusing percent and percentage points. A rise from 80% to 100% is 20 percentage points. Read which one the question asks for.
4. Calculating outside the game. The built-in calculator records your steps, and external software is against the rules of the assessment. Do the math where the game can see it.
5. Starving the mini cases. The study is absorbing, and it is easy to arrive at the cases with eight minutes left. Six cases need about 15.

How Do You Practice Redrock Island?

Practice Redrock Island on full, timed scenarios, because the skill is the whole sequence under one clock, not any single calculation.

Two things can be practiced away from the game. Do short daily drills on percentages, percentage points and growth over several years. And practice reading a dense article for its numbers: pick the ten data points that matter and ignore the rest.

The rest needs the game itself. Prepmatter's McKinsey Solve simulation has 30 Redrock Island scenarios, each with its own brief, exhibits, questions and mini cases. After each one, a performance report shows which answers were right in the Analysis, the Report and the Cases, and a downloadable answer sheet explains how to solve every question.

Updated in November 2026, the simulation covers all three Solve games: 30 Redrock Island scenarios, 30 Sustainable Futures Lab scenarios and unlimited Sea Wolf. You can play one game at a time or all three back to back in the real order and timing. More than 2,200 candidates have used it, and 97% of them passed Solve. If you don't place in the top 30% of the real assessment, Prepmatter refunds 50%: forward your official McKinsey result within two months of purchase.

To see how the simulation and its reports work before you buy, play one full Sustainable Futures Lab scenario in our free McKinsey Solve practice test. Redrock Island itself is part of the full simulation. For a second worked Redrock example, watch Deniz solve the Nolotiles scenario in this earlier video.

The simulation is independently created by Prepmatter and is not affiliated with or endorsed by McKinsey.

How Does Redrock Island Compare to Sea Wolf and Sustainable Futures Lab?

Redrock Island is the only Solve game with a calculator and a report, which makes it the analytical one of the three.

Together, the three games run 95 minutes. For the other two games, see our Sea Wolf guide and our Sustainable Futures Lab guide. For the assessment as a whole, see the full McKinsey Solve walkthrough.

Frequently Asked Questions About Redrock Island

What is Redrock Island in McKinsey Solve?

Redrock Island is the first of the three McKinsey Solve games. You analyze data about an ecosystem in one research study with three stages, Investigation, Analysis and Report, and then solve six short cases.

Is Redrock Island the same as Redrock Study?

Yes. Redrock Study is the earlier name for the same game. Older guides and videos usually call it Redrock Study.

How long is Redrock Island?

Redrock Island runs 35 minutes, covering both the study and the six mini cases. McKinsey Solve as a whole runs 95 minutes: Redrock Island 35, Sea Wolf 30 and Sustainable Futures Lab 30.

How many questions are in Redrock Island?

The study has three to four analysis questions, most with sub-questions, followed by a written report and one chart. After that come six mini cases, each with one or two questions.

Can you use a calculator in Redrock Island?

Yes, the game has a built-in calculator, and you should use it for every calculation. External tools such as Excel are not allowed in McKinsey Solve.

Where can you find Redrock Island answers?

For practice, in Prepmatter's simulation. Every one of its 30 Redrock Island scenarios comes with an answer sheet that explains each question, and a performance report that scores your answers in the Analysis, the Report and the Cases. For the real assessment, no answer key exists, because McKinsey uses its own scenarios and numbers. What carries over is the method.

Can you go back to the data during Redrock Island?

During the Analysis stage, yes. Once you move on to the Report, no. From then on you only have the entries in your Research Journal.

What math do you need for Redrock Island?

Basic arithmetic, percentages, percentage points, growth over several periods and ratios. The numbers are not difficult, but several questions chain steps together.

Can you practice Redrock Island?

Yes. Prepmatter's McKinsey Solve simulation has 30 Redrock Island scenarios with a performance report and an answer sheet for each, alongside 30 Sustainable Futures Lab scenarios and unlimited Sea Wolf.