Suppose that a company ships packages that are variable in weight, with an average weight of 15 lb and a standard deviation of 10. Assuming that the packages come from a large number of different customers so that it is reasonable to model their weights as independent random variables, find the probability that 100 packages will have a total weight exceeding 1700 lb.

Two 5-year girls, Alyse and Jocelyn, have been training to run a 1-mile race. Alyse's 1 mile time A is approximately Normally distributed with a mean of 13.5 and standard deviation of 2.5 minutes. Jocelyn's 1-mile time J is approximately Normally distributed with a mean of 12 minutes and a standard deviation of 1.5 minutes. Assuming A and J are independent random variables, what is the probability that Alyse has a smaller time than Jocelyn in a 1 mile race on a randomly selected day?

The manager of a restaurant believes that waiters and waitresses who introduce themselves by telling customers their names will get larger tips than those who don't. In fact, she claims that the average tip for the former group is 16% while that of the latter is only 12%. If tips are normally distributed with a standard deviation of 8%, what is the probability that in a random sample of 15 tips recorded from waiters and waitresses who introduce themselves and 15 tips from waiters and waitresses who don't, the mean of the former will exceed that of the latter? Probability= 16.75

a) The weights of kindergarten students are known to be normally distributed with a mean of 19.5 kg and a standard deviation of 3.2 kg. Find the probability that exactly 4 out of 11 randomly selected kindergarten students will weigh less than 20 kg.

Suppose that the miles-per-gallon rating of passenger cars is a normally distributed random variable with a mean and a standard deviation of 38.8 mpg and 4.1 mpg, respectively.   What is the probability that a randomly selected passenger car gets at least 45 mpg? What is the probability that a randomly selected passenger car gets between 35 and 40 mpg? An automobile manufacturer wants to build a new passenger car with an mpg rating that improves upon 99% of existing cars. What is the minimum mpg that would achieve this goal?

An engineer is going to redesign an ejection seat for an airplane. The seat was designed for pilots weighing between 130 lb and 191 lb. The new population of pilots has normally distributed weights with a mean of 136 lb and a standard deviation of 34.9 lb a. If a pilot is randomly selected find the probability that his weight is between 130 lb and 191 lb.

The taxi and takeoff time for commercial jets is a random variable x with a mean of 8.4 minutes and a standard deviation of 3.3 minutes. Assume that the distribution of taxi and takeoff times is approximately normal. You may assume that the jets are lined up on a runway so that one taxies and takes off immediately after the other, and that they take off one at a time on a given runway. (a) What is the probability that for 38 jets on a given runway, total taxi and takeoff time will be less than 320 minutes? (Round your answer to four decimal places.)(b) What is the probability that for 38 jets on a given runway, total taxi and takeoff time will be more than 275 minutes? (Round your answer to four decimal places.)(c) What is the probability that for 38 jets on a given runway, total taxi and takeoff time will be between 275 and 320 minutes? (Round your answer to four decimal places.)

Two college roomates have each commited to donating to charity each week for the next year. The roommates weekly incomes are independent of each other. Suppose the amount donated in a week by one roommate is a random variable with mean $30 and standard deviation $10, and the amount donated in a week by the other roommate is a second random variable with mean $60 and standard deviation $20.  Part a.) Find the mean and standard deviation of the distrubution of their combined incomes. Part b.) Over the next year (52 weeks), how many weeks would you expect the two roommates combined income to be more than $120 ?

A semi-truck can transport a maximum of 14,950 pounds. Suppose that a load of cargo containing 115 boxes needs to be transported via this semi-truck. Research has shown that the weights of boxes for this type of cargo have a distribution that has a population mean weight of 125 pounds and a population standard deviation of 20 pounds. Based on this information, what is the probability that all 115 boxes can be safely loaded into the semi-truck and transported?

The taxi and takeoff time for commercial jets is a random variable x with a mean of 8.5 minutes and a standard deviation of 3.2 minutes. Assume that the distribution of taxi and takeoff times is approximately normal. You may assume that the jets are lined up on a runway so that one taxies and takes off immediately after the other, and that they take off one at a time on a given runway. (a) What is the probability that for 37 jets on a given runway, total taxi and takeoff time will be less than 320 minutes? (Round your answer to four decimal places.) (b) What is the probability that for 37 jets on a given runway, total taxi and takeoff time will be more than 275 minutes? (Round your answer to four decimal places.) (c) What is the probability that for 37 jets on a given runway, total taxi and takeoff time will be between 275 and 320 minutes? (Round your answer to four decimal places.)