Test 20, Section 4 (p. 70)


Question 7: You need to weigh the dog's chance of dying from the vaccine against its chance of dying from the disease. But to know the chance of dying from the disease you would need to multiply the mortality rate (which you know is 1/50) by the chance of catching the disease (which you don't know).

Question 11: I do not understand why the argument does not depend on choice E as well as on choice D.

Question 14: Correlation is not causation.

Question 15: The prompt can be written R → P → T. Its contrapositive is ~T → ~P → ~R. (Remember that "Rhonda only if Paul" is equivalent to "If Rhonda then Paul." And "Not Paul unless Ted" is equivalent to "If Paul then Ted.")

Question 20: Senator Armand's expertise in mathematics is not relevant to the topic of land reclamation. Similarly, Lomas's expertise in bike engineering is not relevant to judging who is a better bike racer.

Test 21, Section 2 (p. 88)


Question 4: Here is a rephrase of this question: I played basketball with my brother today. He is much better at shooting baskets than I am. But we each hit 50 out of 100 shots. How could that be? It could be because he took much harder shots than I did.

Question 7: You should understand that the "outskirts of town" is still part of the town, so the "citywide building code" mentioned in choice A would apply in either location. Also, while expanding bus routes (choice C) would be a cost to the city, it would not be a cost for the post office per se.

Question 10: The first sentence tells us that the ratio supply ÷ demand has gone down. The second sentence tells us that supply has gone up. So we know that demand must have gone up as well.

Here is a numerical example: Imagine that last year 100 people wanted to buy oil and there were 50 barrels for sale. The price is the ratio of supply to demand.

Supply: 50
Demand: 100
Price: 100 ÷ 50 = 2

This year, there are 100 barrels of oil for sale, but the price has gone up to 3. What has happened to the demand?

Supply: 100
Demand: ?
Price: Demand ÷ 100 = 3

The demand must have gone up. (In this example, it must have gone up to 300.)

Test 22, Section 4 (p. 138)


Question 21: Terry is assuming that "favorable → good" means that "good → favorable." Pat is assuming that "bad → unfavorable" means "unfavorable → (considered) bad." Both are making the mistake of affirming the consequent.