A random sample of 160 customers at imperial bank revealed t

A random sample of 160 customers at imperial bank revealed that 120 held a checking account and 65 held a savings account. 40 customers had both types of accounts. What is the probability that a customer selected at random had a checking or savings account with the bank?

Solution

P (A) = P( held a checking account ) = 120 / 160 = 0.75

P(B) = P(savings account) = 65 / 160 = 0.41

P(A and B ) = 40 / 160 = 0.25

P(A or B ) = P(A) + P(B) - P(A and B ) = 0.75 + 0.41 - 0.25 = 0.91