Simple probability question, with faulty screws. I have translated the problem as follows:

A factory produces screws, the probability of them being faulty is 0.01 independently. The factory makes a box with 10 screws and recalls the boxes containing 2 or more faulty screws. What is the percentage of boxes that the factory has to recall?


No faulty: $\big(\frac{9.99}{10}\big)^{10} = 0.9900\ldots$
$1$ faulty: $\big(\frac{9.9}{10}\big)^9\times \frac{0.01}{10}=0.0010\ldots$
So the probability is $\approx 0.9$%.
