Suppose that 8 of a certain batch of calculators have a defe

Suppose that 8% of a certain batch of calculators have a defective case, and that 13% have defective batters. Also, 4% have both a defective case and defective batteries. A calculator is selected from the batch at random. Find the probability that the calculator has a good case and good batteries. The probability that the calculator has a good case and good batteries is [ ]. (Type an integer or a decimal)

Solution

let A represents defective case

B represents defective batteries

P( A U B) = P(A) + P(B) - P( A and B)

= 8 + 13 - 4 = 17%

probability that calculator has good case and good batteries

P(A\' and B\') = P( (A U B)\') (using demorgans law)

= 1 - P(A U B)

= 1 - 17%

= 83%