Answer to this probability question

Question

A box 1 contains 5 white balls and 6 black balls .Another box contains 6 white balls and 4 black balls.A box is selected at random
and then a ball is drawn from it
1)what is the probabaility that the ball drawn is white?
2)Given that the ball drawn is white ,what is the probability that it came from box 1?

Answer 1

1)  The probability of selecting either box is 1/2.  

     Box1 P(White) = 5/11

     Box2 P(White) = 6/10

 

     So P(White) = 1/2(5/11) + 1/2(6/10)