lightning fatality rate = 10% (this means that of every 10 people struck, only one will die from the strike).  the probability of two independent events occurring can be calculated by taking product of the probability of each independent event. for example, the probability of events "a" and "b" both occurring can be found by multiplying the probability of event a and the probability of event b. p(a and b) = p(a) * p(b)