Interview Question

Product Marketing Coordinator Interview

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Zenefits

Q: Let’s say that you have 25 horses, and you want to pick the fastest 3 horses out of those 25. In each race, only 5 horses can run at the same time because there are only 5 tracks. What is the minimum number of races required to find the 3 fastest horses without using a stopwatch?

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A: 7 Split them into five groups of five horses and have five races. Then, have a race between the five winners. The winner of this race, call it 1a, is the fastest horse. From its initial race, the second and third horses (call them 2a and 3a) have a chance of being second and third fastest. From the initial race of the horse which arrived second in the winners race (call it 1b), the second horse (call it 2b) has the chance of being third fastest. The horse which arrived third in the winners race (1c) also has a chance of being third fastest. Have an extra race between 2a, 3a, 1b, 2b and 1c. The three fastest horses are 1a and the two winners of this race.

Anonymous on

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This is an incorrect answer. For example, every single horse in the last heat (heat 5) could be faster than the fastest horse in lets say (heat 1). So to solve this you would need to take the top 3 horses from each heat in the case of the above happening. You could then combine into groups of 5 to race and continue the process until you get closer to the end. After race 4 you will have 6 horses and need to dbl race here at this level to make the correct eliminations.

Anonymous on

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