Somebody please help me make some sense out of this: “One morning a certain number of passengers got on an elevator at the main floor of an office building. Four got off at the second floor, of the remainder at the third floor, 75% of the remainder at the fourth floor and 3 at the 5th floor. If the elevator was empty at this point, how many got on the elevator at the main floor?”

The number of chocolate chips in an 18-ounce bag of chocolate chip cookies is approximately normally distributed with a mean of 1252 chips and standard deviation 129 chips. (a) what is the probability that a randomly selected bag contains between 1100 and 1500 chocolate chips, inclusive? (b) what is the probability that a randomly selected bag contains fewer than 1125 chocolate chips? (c) what proportion of bags contains more than 1225 chocolate chips? (d) what is the percentile rank of a bag that contains 1425 chocolate chips?

The u-drive rent-a-truck company plans to spend $13 million on 320 new vehicles. each commercial van will cost $25 comma 000, each small truck $50 comma 000, and each large truck  $80 comma 000. past experience shows that they need twice as many vans as small trucks. how many of each type of vehicle can they buy?

In a singing competition, there are 150 participants. at the end of each round, 40% of the participants are eliminated. how many participants are left after n rounds?