A cement pylon is considered safe if the hairline cracks are spread out and occur on the average of 1.2 cracks per 10-ft length of cement. In a 40-ft section of the cement pylon, what's the probability of 4 or more hairline cracks?

$\displaystyle P(X=x)=\frac{\lambda^xe^{-\lambda}}{x!}$

So $\displaystyle \lambda$ is the average rate (1.2 per 40ft?) and $\displaystyle x$ is the # of events.

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