Mental maths questions for finance interviews
Percentages, quick multiplication, doubling time and estimates, asked without a calculator to see how you think under pressure.
11 questions
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Questions are shown in English, as they are asked in London. You can practise every one of them in English, Spanish, French, German or Italian.
Mental maths
1Quick mental maths: what is 17 times 24?Core
What a strong answer covers
- Answer: 408
- A clear method, e.g. 17 x 25 = 425, minus 17
- Calm, quick delivery
2Revenue grows 10% a year. Roughly how long does it take to double?Core
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- About 7 years
- Rule of 72: 72 / 10 is about 7.2
- Exact answer is about 7.3 years
3What is 15% of 640?Core
What a strong answer covers
- Answer: 96
- Method: 10% is 64 plus 5% is 32
4A share falls 20%. By what percentage must it rise to get back to where it started?Core
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5Roughly, what is 1.08 to the power of 3?Intermediate
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6Brainteaser: what is the angle between the hour and minute hands of a clock at 3:15?Intermediate
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7Paper LBO: we buy a company with EBITDA of 10 at 8x, financed 50% with debt. In five years EBITDA is 15, we exit at 8x and repay no debt. What are the money multiple and the rough IRR?Intermediate
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8I roll a fair die and pay you the number shown in euros. How much would you pay to play? And if you could choose to re-roll once?Intermediate
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9Estimate how many coffees are sold in Spain every day.Intermediate
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10A business has revenue of 200 million and an EBIT margin of 20%. Costs rise 10% while revenue stays flat. What is the new margin?Intermediate
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