Among uses of automated teller machcines ATMs 91 use ATMs to

Among uses of automated teller machcines (ATMs), 91% use ATMs to withdraw cash and 31% use them to check their account balance. Suppose that 95% use ATMs to either withdraw cash or check their account balance (or both). Given a woman who uses an ATM to check her account balance, what the probability that she also uses an ATM to get cash?

Solution

A U B = A + B -2 A intersction B

95 = 91+31 -2 x

x = 13.5 % = 0.135---answer