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RealWorldGraduation_Question_85_Energy_Efficiency   <– PDF

Four people commute to work in the following ways. Person A drives a very fuel efficient car that gets 50 miles to the gallon; he drives alone 75 miles each way to work.  Person B drives alone in an old inefficient pickup truck that gets 12 miles to the gallon; he drives 12 miles each way.  Person C drives a car that gets 25 miles to the gallon.  He drives it alone 5 miles each way to a light-rail station.  There he gets on public light-speed rail; each train consists of 4 cars, and each car holds up to 30 people.  The train is electric, but its energy usage is the equivalent of 2 miles to the gallon, and his commute on the train is 20 miles each way.  Person D takes the city bus 16 miles each way; the bus gets 4 miles per gallon, and holds up to 60 people.  Assume that all the mileages are calibrated to the same blend of gasoline (although they may actually use different fuels).  Which person uses the most efficient means in of energy expenditure in the course of getting back and forth to work?

a) Person A

b) Person B

c) Person C

d) Person D

e) Indeterminate exactly, but it is either Person A or D

(The answer is on p. 2 of the PDF.)

RealWorldGraduation_Question_83_Rat_Sightings   <– PDF

There are 8.143 million (8,143,000) people and an estimated 25 million (25,000,000) rats in the New York City metropolitan area.  Suppose that the estimated rat population is accurate.  The area of the metropolitan area is 322 square miles (8,976,844,800 square feet).  Therefore, density of rats is 25,000,000/8,976,844,800 = .002784 rats per square foot, or one rat for every 359 square feet.    Likewise, the density of people is 8,143,000/8,976,844,000 = .000907 persons per square foot, or one person per 1102.4 square feet.  Since the density of rats is higher, and an area of 359 sq. ft. is a square with sides 18.9 ft long, and since the distance from the center of such a square to any corner (where a person could be) is 26.8 ft, a researcher has concluded (to a first approximation) that a person in New York City is at most (on average) 26.8 ft. from a rat.

On the other hand, another researcher conducted a survey about how often rats are observed in New York City.  Some people reported seeing rats every day, while others could not recall the last time they saw one, even for protracted periods.   A survey was taken in 2002.  In the survey, people were asked if they had seen rats or evidence of rats in their homes in the previous 90 days.  On the upper end, 43% of Hispanic people with income less than $25,000 had seen rats or evidence of them, while only 10% of white people making over $50,000 saw them [1].  Other income levels among whites and Hispanics fell between these two extremes, as did the data for black people of all income levels.

How can these two sets of facts about rats be reconciled?

a) They can be reconciled if one recalls that white people and some upper-class black people have high rates of baseball bat ownership, which rats fear the most.

b) They can be reconciled if one realizes that some people in New York live in expensive neighborhoods and others live in slums because they are victims of the rich. Since rats prefer to live in the poorer neighborhoods because the rodent controls are not as effective, it is logical that some (the poor) see rats every day while others (the rich) never see them.

c) They can be reconciled if one recalls that averages do not apply here because rats prefer to live near people of Hispanic descent because Hispanics throw out a lot of unused vegetables, which are the favorite food of rats.

d) The data can be reconciled because most blacks and nearly all whites will deny or minimize any rat problems in their homes.

e) The data can be reconciled because most Hispanics will exaggerate any rat problems in their homes.

[1]   A. Karpati, B. Kerker, F. Mostashari, T. Singh, A. Hajat, L. Thorpe, M. Bassett, K, Henning, T. Frieden, Health Disparities in New York City, NY: New York City Department of Health and Mental Hygiene, 2004, p. 23