Question

if a box contains 10 left-handed and 20 right-handed screws,what is the probability of obtaining at least one right-handed screw in drawing 2 screws with replacement?

Answer 1

When you take the first screw the odds of getting a left handed one are 1/3 or 10/30

When you take the second screw the odds of getting a left handed one are 9/29

This means that the odds of getting 2 left screws is $\frac{10}{30}$ x $\frac{9}{29}$ = $\frac{3}{29}$

This means that the odds of getting at least one right handed screw is 26/29