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“How many hairstylists or barbers do you estimate there are there in this city? Explain your logic/assumptions.”
Answer: Explain the logic based on the population of the city, average number of cuts people have per year, number of cuts one barber can do per year, and thus how many that implies there must be. (e.g., 2 million people, each get an average of 4 cuts per year, which results in 8 million cuts per year. Each barber works an average of 8 hours per day, times five days per week, times fifty weeks per year equals 2,000 hours of cutting time per year. Each haircut takes 1 hour. Thus, 8 million haircuts, equal 8 million hours, divided by 2,000 hours per barber requires 4,000 barbers in the city.)
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“In the middle of a pond is a single lily pad; the lily pad doubles in size every day and the pond is completely covered on the last day of the month (30 days). How long does it take for the pond to be half covered?”
Answer: 29 days, because if it doubles in size each day it also halves each day. Thus at 29 days is half full in order to be completely full in 30 days.
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“A windowless room contains three identical light bulbs. Each light is connected to one of three switches outside of the room. Each bulb is switched off at present. You are outside the room, and the door is closed. You have one, and only one, opportunity to flip any of the external switches. After this, you can go into the room and look at the lights, but you may not touch the switches again. How can you tell which switch goes to which light?”
Answer: Switch on switches 1 & 2, wait a moment and switch off number 2. Enter the room. Whichever bulb is on is wired to switch 1, whichever is off and hot is wired to switch number 2, and the third is wired to switch 3.
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