# Math Help - Finding probability with only average?

1. ## Finding probability with only average?

A certain type of plastic foil is four feet wide, and has, on average, two ‡flaws in a 100 ft roll. Find the probability that a 20 ft piece has two flaws.

Help please?

2. Originally Posted by Intsecxtanx
A certain type of plastic foil is four feet wide, and has, on average, two ‡flaws in a 100 ft roll. Find the probability that a 20 ft piece has two flaws.

Help please?
Use the Poisson distribution with $\mu = \frac{2}{100} \times 20 = \frac{2}{5}$.