Easy quant question; Can somebody explain?

A local bank reports that 80% of its customers maintain a checking account, 50% have a savings account, and 40% have both. If a customer is chosen at random, what is the probability the customer has only one account, either a checking account or a savings account?

Think Venn Diagram for this… 80 customers are having Checking Account 50 customers are having Saving Account 40 are having both therefore, Customers only having Checking Account are = 80 - 40 = 40 Customers only having Saving Account are = 50 - 40 = 10 Total customers have just one account (be it Saving or Checking, we don’t care) = 40 + 10 = 50 So out of total 100 customers, 50 are having just 1 account. Hence probablilty should be 50/100 = 0.5 - Dinesh S

dinesh is right or you can think of it like this 40% have both that means that 60% have one or none 1-80%=20% percentage of ones that dont have savings 1-50%=50% percentge that don’t have checking 0.2*0.5=10% percentage that have either 60%-10%=50% percentage that have at least one acc

Thanks Dinesh