Asmall train at an amusement park is carrying passengers. half of the passengers are 4 years old, 1/10 are 5 years old, 3/10 are 6 years old, and 1/10 are 7 years old. what is the expected age for one of the passengers on the train? a. 5 yearsb. 5.5 yearsc. 6 yearsd. 6.1 years

On saturday morning, calls arrive at ticketmaster at a rate of 108 calls per hour. what is the probability of fewer than three calls in a randomly chosen minute?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?