Investment Banking puzzles, solved step by step

About 2 crore a year. India has about 140 crore people in roughly 30 crore households. If about half of households own a two-wheeler, 15 crore are in use. A vehicle lasts about 10 years, so 1.5 crore are replaced each year, and a fleet growing 3% adds about 45 lakh more, close to 2 crore. A top-down check, 18 crore vehicles on the road over a 9-year life, lands at 2.0 crore too. The published industry figure is the thing to confirm, not to recall.

Where do you start, and what do you refuse to guess?

Think of guessing how many birthday cakes a town buys in a year. Nobody knows the number, but everybody can picture the pieces: people, birthdays per person, the share with a cake. Market sizing works from a number you can picture to the number you cannot, and the only figure taken on trust is the population. About 140 crore people at 4.5 per household is 31 crore households, call it 30. The one real judgement is the ownership rate, the penetrationThe share of possible buyers who already own the product. Half of households here.: higher in towns, lower in villages, so about half overall.

How does the bottom-up build go?

Thirty crore households at 50% is 15 crore two-wheelers in use. Sales are what it takes to keep that fleet going plus what it takes to grow it. Yearly sales of a durable are the fleet divided by its life, plus the fleet's growth, so the life assumption matters as much as the ownership rate. At a 10-year life, 1.5 crore are replaced each year; a fleet growing 3% a year needs another 45 lakh; together about 1.95 crore. Say each assumption as you use it, so the interviewer can push on the one they disagree with.

Why build a second route, and what if it disagrees?

Come at it from the fleet instead. About 13 two-wheelers per 100 people is 18 crore on the road, and dividing by a 9-year average life gives 2.0 crore a year, within 4% of the first route. A demand estimate is credible only once an independent route lands near it; agreement does not prove either number, but disagreement tells you which assumption to revisit. Stress the two judgements: 40% ownership and a 12-year life give 1.4 crore, 60% and 8 years give 2.8 crore. So the honest answer is a range of about 1.5 to 3 crore with 2 crore most likely, and the published sales figure from the industry body is the check to look up afterwards.

Roughly 34,050 to 41,950, with about two-thirds confidence. Four months is a third of a year, and volatility scales with the square root of time, so 18% a year becomes 18% times 0.577, about 10.4%, over four months. One standard deviation is about 3,949 points either side of 38,000. If returns are roughly normal, about 68% of outcomes land inside that band and about 95% inside 30,100 to 45,900. Give the range and the confidence, never a single number.

Why does volatility shrink with the square root of time?

Picture someone leaving a party and taking steps at random, forward or back. After four steps they are not four steps from the door; some steps cancelled, and on average they are about two away. Random moves partly cancel, so the spread of where you end up grows with the square root of the number of moves, not with the number itself. Four months is a third of a year, the square root of a third is 0.577, and 18% times 0.577 is 10.4%. Dividing 18% by three to get 6% would be right only if every month moved the same way, which is the opposite of random.

How do you turn 10.4% into a range?

10.4% of 38,000 is about 3,949 points. One standard deviationA measure of how far outcomes typically land from the centre. Under a normal distribution about 68% of outcomes fall within one of the centre and 95% within two. either side is 34,050 to 41,950; two is 30,100 to 45,900. A one standard deviation band is a two-in-three bet, so the confidence attached to the width is the answer, and a range without one is just a guess with margins. Say the band, say the two in three, and offer the wider nineteen-in-twenty band if the interviewer wants more certainty.

What do you add to sound like a trader rather than a textbook?

Three refinements, each one sentence. Returns compound, so the band is slightly lopsided: 38,000 grown and shrunk by 10.4% continuously is about 34,250 to 42,150, a little more room on the upside. The expected drift over four months is a percent or two, small next to 10.4%, so ignoring it is fair. Real markets have fatter tails than the bell curve, so the two standard deviation band gets breached more often than one time in twenty. Say the range, say the confidence, then say what would make you wrong: the 18% itself is a historical figure, and the volatility the options market implies for the next four months may be higher or lower. This is a way of describing uncertainty, not a forecast, and the interviewer is testing whether you think in distributions.

The game is worth Rs 4.25 lakh, and you roll again on a 1, 2 or 3. A single roll is worth 3.5 lakh on average, so the chance to roll again is worth exactly that. Keep any first roll above 3.5, which means 4, 5 or 6. Half the time you keep, averaging 5 lakh; half the time you roll again for 3.5. Half of 5 plus half of 3.5 is 4.25 lakh. The option to re-roll adds 0.75 lakh over a single roll.

Why is the rule to compare against 3.5?

Think of boarding a train with one visible seat by the door and the rest of the carriage out of sight. You walk on only if the seat you can see is worse than the average seat down the carriage, because once you walk you take whatever is there. Work backwards: the last decision has no choices left, so its value is the plain average, 3.5 lakh, and any earlier roll is kept only if it beats that. A 4, 5 or 6 beats 3.5; a 1, 2 or 3 does not; no face equals it, so the rule has no ties. The number you are comparing with is the expected valueThe average outcome if the same gamble were repeated many times: each result weighted by its probability. of rolling again.

How does the 4.25 come together?

Three faces out of six are kept and contribute (4 + 5 + 6) over 6, which is 2.5 lakh; three are re-rolled and contribute three sixths of 3.5, which is 1.75; the total is 4.25 lakh. Check the rule by moving it. Keep the 3 as well: (3 + 4 + 5 + 6) over 6 plus two sixths of 3.5 is 4.17. Re-roll the 4 too: (5 + 6) over 6 plus four sixths of 3.5 is 4.17. Both sit below 4.25, about Rs 8,333 a game, so 3.5 is the only bar that gives the full value.

What happens with a third roll, and why do interviewers ask?

Allow two re-rolls. The game from the second roll onward is now worth 4.25, so on the first roll you keep only a 5 or 6: (5 + 6) over 6 plus four sixths of 4.25 is 4.67 lakh. Every extra chance to try again raises both the value of the game and the bar for stopping, and that is the whole logic of an option: the right to swap a known result for an uncertain one is worth paying for only when the known result is poor. The same reasoning prices walking away from a signed deal or waiting for a better bid. The limit: this assumes you care only about the average. Someone who badly needs 3 lakh might keep a 3, and that is a preference, not an error.

Only the balance sheet changes. Property, plant and equipment rises by Rs 100 crore and accounts payable rises by Rs 100 crore, so both sides grow by the same amount. No cash has moved, so the cash flow statement is untouched, and no time has passed for depreciation, so the income statement is untouched too. Cash and capex appear in 60 days, when the supplier is paid.

Why does a purchase on credit touch neither cash nor profit?

Think of buying a refrigerator on a shop's 60-day credit. The fridge is in your kitchen today and you owe the shop, but your bank balance has not moved and nothing has come out of this month's budget. A credit purchase adds an asset and a debt of the same size, so the balance sheet grows on both sides and nothing else moves. The machine will be used for years, so its cost is not an expense on the day it arrives. It reaches the income statement slowly, through depreciation, over the years it is used.

What happens over the next 60 days and beyond?

Day 60 is when the cash flow statement wakes up. The company pays the supplier: cash falls by 100 and payables fall by 100. The Rs 100 crore appears as capital expenditure in investing cash flow in the year it is paid, not the year the machine arrived. The notes to the accounts usually flag the year-end purchase as a non-cash investing item, so a reader is not surprised. From the following year, depreciation starts: on a 10-year straight line, Rs 10 crore a year comes off pre-tax profit, is added back in operating cash flow, and lowers the machine's book value.

Close by saying the balance check out loud. Assets up 100, liabilities up 100: the sheet balances, and that one sentence tells the interviewer you walk the statements in a fixed order rather than guessing. Interviewers use small timing questions like this one to see whether you separate when something is owned, when it is paid for and when it is expensed.

204 squares. A square of side k can start in (9 minus k) columns and (9 minus k) rows, so there are 64 squares of size 1, 49 of size 2, 36 of size 3, and so on down to a single 8 x 8. The total is the sum of the first eight square numbers, 1 + 4 + 9 + ... + 64, which is 204.

How do you count one size without listing every square?

Picture sliding a 3 x 3 photo frame across the board. Its left edge can sit on column 1, 2, 3, 4, 5 or 6; on column 7 it would hang off the side. That is 6 positions across and, by the same logic, 6 down. Count where a square's top-left corner can sit, not the squares themselves: a k x k square has (9 minus k) choices in each direction, so (9 minus k) squared positions. For k = 3 that is 36, for k = 7 it is 4, and the whole board is the single 8 x 8.

How do you add 64 + 49 + ... + 1 quickly?

Add from the top and say the running total: 64 and 49 is 113, plus 36 is 149, plus 25 is 174, plus 16 is 190, then 9, 4 and 1 take it to 204. If you know the formula for a sum of squares, use it as a check rather than a starting point. The interviewer scores the moment you see that each size contributes a square number, not the formula you remember.

Why is 1,296 the wrong answer here?

1,296 is the number of rectangles of every shape. A rectangle is fixed by choosing two of the 9 vertical grid lines and two of the 9 horizontal ones, 36 ways each, and 36 x 36 is 1,296. Squares are the rectangles whose two sides are equal, which is why the count falls from 1,296 to 204. Offering that link unprompted shows you understand the counting rather than a memorised trick.

The WACC is 11.4%. Equity is 60% of the funding at 14%, contributing 8.4 points. Debt is 40% at 10% before tax, but interest is tax-deductible, so its after-tax cost is 10% x (1 minus 25%) = 7.5%, contributing 3.0 points. Add them: 8.4 + 3.0 = 11.4%. Leaving out the tax shield gives 12.4%.

Why is it a weighted average and not a plain one?

A family buying a flat with 60% from savings and 40% from a home loan pays a blended cost that leans towards the bigger source. Each source of money counts in proportion to how much of the funding it provides. Here equity provides 60 rupees in every 100, so its 14% carries more weight than debt's rate. A plain average of 14% and 10% would be 12.0%, which pretends the two sources are the same size.

Why does debt go in after tax?

Interest is deducted before profit is taxed, so every 10 rupees of interest cuts the tax bill by 2.50 rupees at a 25% rate. The tax saved pays a quarter of the interest, so the company's true cost of debt is 7.5%, not 10%. That saving is the tax shieldThe tax a company avoids because interest is deducted from profit before tax is worked out.. Equity has no such shield, because dividends are paid out of profit after tax, which is why the adjustment sits on the debt term only.

One more sentence wins the point. The weights should be market values, not the book values on the balance sheet, because investors demand a return on what their stake is worth today. Then say what the number is for: 11.4% is the rate at which you would discount the company's unlevered free cash flows in a DCF.

42. The gaps between terms are 4, 6, 8 and 10, rising by 2 each time, so the next gap is 12 and 30 + 12 = 42. The rule underneath is that the nth term is n x (n + 1): 1 x 2, 2 x 3, 3 x 4, 4 x 5, 5 x 6, and next 6 x 7, which is 42.

What should you do first with any number series?

Imagine a taxi meter that charges a little more for each extra kilometre than it did for the one before. The fares look irregular, but the jumps between them tell the story. Write the differences between terms underneath the series before guessing, and if they are not constant, take differences again. Here the first differences are 4, 6, 8 and 10, and the second differences are a steady 2, which tells you the rule is a quadratic: something times something.

How do you check the answer, not just find it?

A second route that lands on the same number is your proof. Each term splits into two neighbouring whole numbers: 2 = 1 x 2, 6 = 2 x 3, 12 = 3 x 4, 20 = 4 x 5, 30 = 5 x 6. Two methods agreeing, differences and a formula, turn a guess into an answer. The formula also lets you jump ahead: the 10th term is 10 x 11 = 110 without writing out the terms in between.

Why does a bank put this in an online test?

Numerical and logical screens are timed tightly and filter large numbers of applicants before anyone reads a CV. The skill being tested is spotting structure fast, the same skill you use when a line in a model grows by a changing amount each year. A revenue line whose yearly increase itself rises by a fixed amount has exactly this shape, and seeing it saves you from projecting the last increase forward as if it were fixed.

About 2.67%. A P/E of 15 means each Rs 100 of share price buys Rs 6.67 of yearly earnings, an earnings yield of 1 over 15. The company pays out 40% of that, Rs 2.67, as dividend. Dividend yield is dividend over price, Rs 2.67 over Rs 100. In one line: the payout ratio divided by the P/E, 0.40 over 15.

How do you turn a P/E into something you can multiply?

Flip it. A P/E of 15 says you pay 15 rupees for every rupee of yearly profit, so every rupee of price buys one fifteenth of a rupee of profit. Inverting the P/E gives the earnings yieldEarnings per share divided by the share price: the inverse of the P/E., 1 over 15 or about 6.67%, and every other per-share ratio then falls out by multiplication. Picking a round share price of Rs 100 makes it concrete: earnings per share are Rs 6.67.

Why is the dividend only part of the shareholder's return?

Think of a shopkeeper who takes home 40% of each year's profit and leaves 60% in the shop to buy more stock. The retained Rs 4.00 is not lost to shareholders; it is reinvested, and if it earns a decent return it should lift future earnings and dividends. That is why a low dividend yield on its own says little about whether a share is cheap. A company paying out everything would show a 6.67% yield and little room to grow.

Say the general rule after the number, because the follow-up usually changes one input. If the P/E doubles to 30 with the same payout, the yield halves to 1.33%; if the payout doubles to 80% at the same P/E, the yield doubles to 5.33%. Having the one-line formula ready means you answer those in a breath.

Option two, by about 10 points: roughly 34.8% against 24.6%. Option one triples the money in five years, so its IRR is 3 to the power of one fifth, minus 1, about 24.6%. Option two returns a third of the proceeds in year 2. Test 35%: the year-2 cheque is worth 54.9 today and the year-5 cheque 44.6, together 99.5, just under 100, so the IRR is a shade under 35%.

Why does the same multiple give two different IRRs?

Imagine lending a friend Rs 100 and getting Rs 300 back. If the Rs 300 arrives in one go after five years, fine. If Rs 100 comes back after two years, you have your stake back early and can lend it again. The money multiple counts rupees; the IRR counts rupees and how long each one spends away from you. Option two returns a third of the proceeds three years sooner, so the money is tied up for less time on average and the yearly rate is higher.

How do you get the second IRR without a calculator?

Option one is clean. You know 2x in five years is about 15% a year and 3x is about 25%, and the exact figure is 24.6%. Option two has no neat formula, so pick a round guess and test it. At 35%, the year-2 cheque is worth 100 over 1.35 squared, about 54.9, and the year-5 cheque is worth 200 over 1.35 to the fifth, about 44.6: 99.5 in total, just short of the 100 invested, so the IRR sits just under 35%. One trial, said out loud, is all the interviewer needs.

Why do sponsors like recaps, and what is the catch?

Funds are often judged on IRR, so pulling cash out early through a dividend recapThe company borrows new debt and pays the money out to its owners as a dividend. lifts the number without changing the multiple. The catch is that the recap is paid for with new borrowing, so the company carries more debt for its last three years and the exit equity is smaller and riskier. A strong answer names all three effects: a higher IRR, the same multiple, more leverage. IRR rewards speed and the multiple rewards size, and investors look at both.

107 crore diluted shares. Only options with a strike below the Rs 50 share price are exercised. The Rs 20 tranche brings in Rs 200 crore, which buys back 4 crore shares, so it adds 6 crore net. The Rs 40 tranche also brings in Rs 200 crore, buying back 4 crore, so it adds 1 crore net. The Rs 60 tranche is out of the money and adds nothing.

Why do only some options count?

An option to buy a share at Rs 60 when it trades at Rs 50 is like a voucher to buy a shirt for more than its shelf price: nobody uses it. Only in-the-money options, those with a strike below the current share price, would be exercised, so only they add shares. Here the Rs 20 and Rs 40 tranches are in the money and the Rs 60 tranche is not. The 8 crore Rs 60 options are ignored today, but they come back into play if the price rises past Rs 60 or a bidder offers more than that.

Why does each tranche add fewer shares than its option count?

When holders exercise, they pay the strike price to the company. The treasury stock methodA way to count dilution that assumes the company uses the cash from option exercises to buy back its own shares at the current price. assumes the company uses that cash to buy back shares at today's price. Each in-the-money tranche adds its option count minus the shares its exercise cash can buy back. The Rs 20 tranche pays 10 crore x Rs 20 = Rs 200 crore, which buys 4 crore shares at Rs 50, so 6 crore net. The Rs 40 tranche pays 5 crore x Rs 40 = Rs 200 crore, again 4 crore bought back, so 1 crore net.

Notice what the formula says. The deeper in the money an option is, the closer it comes to a full new share: the Rs 20 tranche dilutes at 60% of its count, the Rs 40 tranche at only 20%. Diluted equity value at Rs 50 is 107 crore x Rs 50 = Rs 5,350 crore, Rs 350 crore above the basic Rs 5,000 crore, and that diluted figure is the one that goes into an enterprise value bridge.