I was visiting a friend one evening and remembered that he had three daughters. I asked him how old they were. “The product of their ages is 72,” he answered. Quizzically, I asked, “Is there anything else you can tell me?” “Yes,” he replied, “the sum of their ages is equal to the number of my house.” I stepped outside to see what the house number was. Upon returning inside, I said to my host, “I’m sorry, but I still can’t figure out their ages.” He responded apologetically, “I’m sorry, I forgot to mention that my oldest daughter likes strawberry shortcake.” With this information, I was able to determine all three of their ages. How old is each daughter?
The house number alone would have identified any of these groups. Since more information was required, we know the sum left the answer unknown. The presence of a single oldest child eliminates “2 6 6”, leaving “3 3 8” as the only possible answer.
What does man love more than life Fear more than death or mortal strife What the poor have, the rich require, and what contented men desire, What the miser spends and the spendthrift saves And all men carry to their graves?
This is a most unusual paragraph. How quickly can you find out what is so unusual about it? It looks so ordinary you’d think nothing was wrong with it – and in fact, nothing is wrong with it. It is unusual though. Why? Study it, think about it, and you may find out. Try to do it without coaching. If you work at it for a bit it will dawn on you. So jump to it and try your skill at figuring it out. Good luck! Don’t blow your cool!
Imagine an HIV test that is 95% accurate (false positive rate of 5%) and around 2% of the tested population is infected with HIV. What is the probability that you actually have HIV when your test comes back positive?