Find D₆,D₈,P₇ and P₂₀ for the data 57, 58, 61, 42, 38, 65, 72, 66. 

In a Shooting test, the probabilities of hitting the target are \(\frac { 1 }{ 2 } \) for A, \(\frac { 2 }{ 3 } \) for B and \(\frac { 3 }{ 4 } \)  for C. If all of them fire at the same target, calculate the probabilities that only one of them hit the target.

A factory has 3 machines A₁, A₂, A₃ producing 1000, 2000, 3000 bolts per day respectively. A₁ produces 1% defectives, A₂ produces 1.5% and A₃ produces 2% defectives. A bolt is chosen at random and found defective. What is the probability that it comes from machine A₁?

There are 3 boxes containing respectively 1 white, 2 red, 3 black balls; 2 white, 3 red and 1 black ball; 2 white, 1 red, 3 black balls. A box is chosen t random and from it 2 balls are drawn at random. The 2 balls are 1 red and 1 white. What is the probability that they come from the second box?

A box contains 4 red, 6 green balls. Two balls are picked out one by one at random without replacement. What is the probability that the second is green given that the first one is green?