Recently a study was published that stated that: "40% of children are subjected to tobacco smoke in their home."

If we assume that all households consist of a father and a mother and one or more children, that children do not smoke and that smoking rates are the same for men than for women,

**What percentage of adults are smokers?**

#### Solution

The probability of receiving tobacco is that at least one of the parents is a smoker. This is equal to the sum of both probabilities minus their product (probability that both are). That is, if x is the smoking rate:

2x - x^{2} = 0,40

From where we easily get that x = 0.225, that is, **22.5% of adults are smokers**.