I got this puzzle from my brother-in-law today (all your jokes about troubles created by inlaws to be inserted here 🙂 ). I believe I have arrived at the right answer but since he does not know the answer himself, would like to see if others can prove or disprove me.
A car’s wear and tear pattern is such that any new tire put in the front can last 40,000 miles and the ones in the rear can last 60,000 miles. You are given four new tires to begin with and you can interchange the tires between front and rear as many times as you want. What is the maximum distance you can drive?

Strictly speaking, it is not puzzle time since I am flying out of Atlanta not to Atlanta. But what the hell, it is holiday season… so, here goes..
I was addressing a large audience this morning and asked those who have two kids to raise their hands. Then I asked – of all the people who have their hands raised – to keep their hands raised if one of their child is a son born on a Sunday. They rest can put their hands down. Now I picked any one from the ones left with their hands raised. What is the probability that their other child is a son?
(assume equal probability for having a son or a daughter or which day of the week a child is born).