Investment Banking interview preparation
Every question below is either traced to a named firm from a public candidate report, or tagged at desk level when we could not trace it. Answers are written the way you would actually say them out loud — answer first, then the mechanism, then the limitation.
100 questions, mapped to the firms that asked them
- Questions
- 100
- Traced to a firm
- 100
- Firms
- 46
- Updated
- September 2026
055If I make 8 times my money in 6 years, what is my IRR?Warburg PincusPrivate Equity · New York · 2012
Say this
About 41 percent. Eight times is two doublings and a bit: 2 times is 100 percent, 4 times is 300 percent, 8 times is 2 cubed, so the money doubles three times in six years, which is a doubling every two years. A doubling in two years is about 41 percent a year.
Then walk it
- Reframe 8 times as 2 to the power of 3. Three doublings in six years means one doubling every two years.
- The rule of 72 in reverse: 72 divided by 2 years is 36, so roughly 36 percent. That gets you close, and the precise answer is 41 percent because the rule of 72 is an approximation.
- Exact check: 1.41 squared is 2, so a 41 percent annual return doubles money in two years, and three of those gives 8 times.
- Worth memorising the grid, because these come up constantly: 2 times in 5 years is 15 percent, 2.5 times in 5 years is 20 percent, 3 times in 5 years is 25 percent, 2 times in 3 years is 26 percent.
- Then say the practical caveat: IRR is time-weighted, so an early dividend recap flatters it. Money multiple and IRR can disagree, and sponsors quote whichever looks better.
Where candidates lose it
Trying to compute the sixth root arithmetically and stalling. Decompose the multiple into powers of two and use doublings. Interviewers are testing mental agility and whether you know the standard IRR grid cold.
Expect next
- Which is better, 25 percent IRR over 5 years or 30 percent over 3?
- Why can IRR and money multiple disagree?
- How does a dividend recap affect IRR?
Reported by candidates at Warburg Pincus (Private Equity, New York, 2012). Source: Wall Street Oasis.
056Which yields a greater return, an IRR of 25 percent over 5 years or an IRR of 30 percent over 3 years?Centerview PartnersGeneralist · New York · 2026
Say this
The 25 percent over five years returns more total money: about 3.05 times against about 2.2 times. But the 30 percent is the better rate of return, so the answer depends on whether you can redeploy the capital.
Then walk it
- 1.25 to the fifth is roughly 3.05 times. 1.3 cubed is roughly 2.2 times. So more absolute money from the longer hold.
- But IRR is an annualised rate, and 30 percent beats 25 percent per year of capital employed.
- The deciding question is reinvestment. If you can put that capital straight into another 30 percent deal for the remaining two years, the short hold wins comfortably: 2.2 times 1.69 is about 3.7 times.
- If the capital sits in cash for two years, the long hold wins.
- This is exactly why limited partners care about both IRR and multiple on invested capital, and why a fund with spectacular IRR from fast flips can return less cash than one with lower IRR and longer holds.
Where candidates lose it
Answering with only one of the two framings. The question is deliberately ambiguous, and the right move is to compute both, then name reinvestment risk as the thing that decides it.
Expect next
- So which would a limited partner prefer?
- Why do funds report both IRR and MOIC?
- How would you game an IRR?
Reported by candidates at Centerview Partners (Generalist, New York, 2026). Source: Wall Street Oasis.
081How would you value your favourite animal?Rothschild & CoGeneralist · New York · 2026
Say this
Pick an animal with an obvious cash flow so the question becomes tractable. A racehorse: value it on prize money, breeding fees and resale, less training and stabling costs, discounted over its career.
Then walk it
- Choose the animal strategically. A racehorse, a dairy cow or a breeding bull all have identifiable revenue. A panda does not, and you will spend the whole answer fighting your own example.
- For a racehorse: expected prize money, weighted by the probability of winning at each grade, plus stud fees after retirement, which for a successful stallion dwarf the racing income.
- Costs: training fees, stabling, vet, insurance, jockey and entry fees. These are substantial and largely fixed, so most horses are value-destructive.
- Finite life with a terminal value: the residual breeding or resale value at the end of the racing career.
- Then the honest framing, which is the point of the question: the expected value is the probability-weighted average of a few enormous outcomes and many zeros. It is an option, not an annuity, so the way to value it is scenario-weighted, and the market price of a yearling at auction is your best cross-check.
Where candidates lose it
Freezing on the absurdity, or picking an animal with no cash flow and then trying to force a DCF onto it. Reframe the question as 'value any finite-life risky asset', choose an example that cooperates, and name your framework before you touch any number.
Expect next
- What is your personal beta?
- How would you value a business with the same payoff shape?
- How would you cross-check your number?
Reported by candidates at Rothschild & Co (Generalist, New York, 2026). Source: Wall Street Oasis.
092I paint the surface of a 10x10x10 cube green. How many of the small cubes have green on them, and how many do not?TD SecuritiesGeneralist · New York · 2024
Say this
488 have green on them and 512 do not. Solve the easy half first: the unpainted cubes form an inner 8x8x8 block, which is 512. Subtract that from 1,000 to get 488 painted.
Then walk it
- Total small cubes: 10 cubed is 1,000.
- Any cube not touching the surface is one layer in from every face. That leaves an 8 by 8 by 8 core, because you remove one layer from each of the two opposite sides in all three dimensions.
- 8 cubed is 512 unpainted.
- So painted is 1,000 minus 512, which is 488. Computing the painted faces directly is possible but far more error-prone.
- If they push further: 8 corner cubes have three painted faces, 96 edge cubes have two, and 384 face cubes have one. That sums to 488, which confirms the answer.
Where candidates lose it
Trying to count the painted cubes face by face and double-counting the edges and corners. Always solve for the interior and subtract. Saying 'I will do the easy side first' out loud is itself the signal they want.
Expect next
- How many have exactly two painted faces?
- Generalise it for an n-cube.
- Now do it for a 10x10x10 where I only paint the top and bottom.
Reported by candidates at TD Securities (Generalist, New York, 2024). Source: Wall Street Oasis.
094How many aeroplanes are in the air at once?Société GénéraleMergers and Acquisitions · New York · 2025HSBCSales and Trading · Hong Kong · 2026
Say this
Around ten to fifteen thousand. Build it from the fleet: roughly 25,000 commercial aircraft worldwide, each flying maybe 10 hours a day, so about 40 percent are airborne at any moment, which gives 10,000.
Then walk it
- Start from a number you can defend: the global commercial fleet is on the order of 25,000 aircraft. If you do not know it, build it from airlines: a few hundred carriers averaging perhaps 80 aircraft.
- Utilisation: a commercial jet flies roughly 8 to 12 hours a day. Call it 10, which is about 40 percent of a 24-hour day.
- 25,000 times 0.4 gives 10,000 airborne on average.
- Then adjust for the peak-trough pattern. Air traffic is concentrated in daylight hours across the Northern Hemisphere, so the daytime peak might be 50 percent above average and the small hours well below. Peak perhaps 15,000.
- Then say what you excluded and why: private aviation, cargo and military would add to it, probably a few thousand more, and I have not counted them.
- Close with the sanity check: published flight-tracking figures sit in the same range, low to mid five figures, so the estimate holds.
Where candidates lose it
Guessing a number with no derivation, or getting lost in decimals. Market sizing is judged entirely on structure. State each assumption, keep the arithmetic round, and say which populations you left out.
Expect next
- How many taxis are in Hong Kong Central?
- How many hotel beds are there in New York City?
- How many books were sold in the US last year?
Reported by candidates at Société Générale (Mergers and Acquisitions, New York, 2025); HSBC (Sales and Trading, Hong Kong, 2026). Source: Wall Street Oasis.
095What is 301 times 447?General AtlanticGeneralist · New York · 2026
Say this
134,547. Break 301 into 300 plus 1. Three hundred times 447 is 134,100, plus one more 447 gives 134,547.
Then walk it
- Decompose to the nearest round number. 301 is 300 plus 1, and 300 is easy because it is 3 times 100.
- 447 times 3 is 1,341. Times 100 is 134,100.
- Add the remaining 447: 134,547.
- Announce the decomposition before you compute, so the interviewer can follow and so a slip in arithmetic does not look like a failure of method.
- The same trick handles most of these: round one number, multiply, then correct. For 19 times 63, do 20 times 63 minus 63.
Where candidates lose it
Attempting long multiplication in your head and losing a digit. These are speed-and-method tests. Decompose out loud, keep one running total, and offer the sanity check that the answer should be a bit over 134,000.
Expect next
- What is 19 times 63?
- What is 1/7 as a decimal?
- What is the square root of 6,241?
Reported by candidates at General Atlantic (Generalist, New York, 2026). Source: Wall Street Oasis.
Firm tags come from public, anonymous candidate reports on Wall Street Oasis: strong signal, not sworn testimony. Firms are named as the places a question was reported, not as partners of Fin Maverick. Answers are written for this page to show how to think out loud; they are not scripts to recite.