My problem says that 1 out of 2 people in the neighborhood have a car. How many people out of 100 neighbors have a car? I don't understand what that means. First they say 2 people then 100...

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Please provide a clearer title. Everybody needs help here –  John Smith Mar 9 '12 at 22:07
If you would walk your neighborhood, on average, every second house would have a car parked next to it. How many cars would you count if you have passed 100 houses on your walk? –  dtldarek Mar 9 '12 at 22:11
1 out of 2 is an English language expression, the rest is as @AméricoTavares says. This fact must have been collected after analysis of data but it does not tell you how many people are in the neighborhood because it is just a percentage. –  Emmad Kareem Mar 9 '12 at 22:11

If out of $2$ neighbors you have $1$ neighbor that owns a car, then out of $100$ neighbors there are $50$ neighbors with a car. The statement of the question states that the ratio of "neighbors with a car" with respect to "neighbors" is a half. Therefore, to know how many neighbors out of $100$ have a car, you compute "half of $100$".
I'd say the number of neighbors with a car $X$ is distributed as $X \sim \mathrm{Bin}(100,0.5)$ (and so $X$ is unknown), but maybe I'm making things too complicated then... –  TMM Mar 10 '12 at 1:43