9 questions

Brainteasers & mental math

Market sizing, probability puzzles and arithmetic without a calculator.

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Core 6

  1. 01 How would you estimate the number of petrol stations in the UK? Frequently askedInternAnalyst
  2. 02 How do you multiply 48 by 52 in your head? InternAnalyst
  3. 03 What is the sum of all the numbers from 1 to 200? Intern
  4. 04 What is the angle between the hands of a clock at 9:45? Intern Plus
  5. 05 What is the probability that two cards drawn from a deck are the same suit? InternAnalyst Plus
  6. 06 A lily pad doubles in size every day and covers a pond in 30 days. When does it cover half? Intern Plus

Intermediate 3

  1. 01 You have nine balls, one slightly heavier, and a balance. How do you find it in two weighings? InternAnalyst Plus
  2. 02 How would you split 40 red and 40 blue balls between two jars to maximise the chance of drawing a red one? InternAnalyst Plus
  3. 03 You drive 60 km at 30 km/h. How fast must you drive the next 60 km to average 60 km/h? InternAnalyst Plus