Two Questions That’ll Make You Think
posted at 8:22 pm
on Nov. 27, 2006
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Day 7: The Water Advisory Is Over
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Whoever gets the most correct answers, or closest to the correct answers, for these questions, gets a free copy of Dreamweaver 8 All-in-One desk reference, retail value $45 Canadian. Plus that person will get recognition from me as being really really smart.
1. A cab was involved in a hit and run accident at night. Two cab companies, the Green and the Blue, operate in the city. You are given the following data:
85% of the cabs in the city are Green and 15% are Blue.
A witness identified the cab as Blue. The court tested the reliability of the witness under the same circumstances that existed on the night of the accident and concluded that the witness correctly identified each one of the two colors 80% of the time and failed 20% of the time.
What is the probability that the cab involved in the accident was Blue rather than Green? (Please feel free to estimate if you’d like.)
2. You have two ropes, two sticks, and a lighter. You know that if you light the rope, it will take one hour to burn. However, it doesn’t necessarily burn at the same rate all hour long. It might burn slowly for 55 minutes, then consume the rest of the rope in 5 minutes.
You need to know when exactly 15 minutes has elapsed. How do you do it?
