单选题
Directions: Questions 9-20 have three different formats.
Unless a question has its own directions that specifically state otherwise, each
question has five answer choices, exactly one of which is correct.
单选题
The Center City Little League is divided into d divisions. Each division has t teams, and each team has p players. How many players are there in the entire league?
【正确答案】
B
【答案解析】Since d divisions each have t teams, multiply to get dt teams; and since each team has p players, multiply the number of teams (dt) by p to get the total number of players: dtp.
**Use TACTIC 2, Chapter 8. Pick three easy-to-use numbers for t, d, and
p. Assume that there are 2 divisions, each consisting of 4 teams, so, there are 2 × 4 = 8 teams. Then assume that each team has 10 players, for a total of 8 × 10 = 80 players. Now check the choices. Which one is equal to 80 when d= 2, t= 4, and p = 10? Only dtp.
单选题
In 1980, the cost of p pounds of potatoes was d dollars. In 1990, the
cost of 2p pounds of potatoes was 
【正确答案】
C
【答案解析】Since, in 1990, 2p pounds of potatoes cost[*]d dollars, p pounds cost
[*]
**In this type of problem it is often easier to use TACTIC 2, Chapter 8. Assume that 1 pound of potatoes cost $100 in 1980. Then in 1990, 2 pounds cost $50, so 1 pound cost $25. This is a decrease of $75 in the cost of 1 pound of potatoes, and
[*]
填空题
Directions:The answer to the following question is a fraction. Enter the numerator in the upper box and the denominator in the lower box A number x is chosen at random from the set of positive integers less than 10. What is the probability that 
单选题
A bag contains 3 red, 4 white, and 5 blue marbles. Jason begins
removing marbles from the bag at random, one at a time. What is the least number
of marbles he must remove to be sure that he has at least one of each color?
【正确答案】
D
【答案解析】If Jason were really unlucky, what could go wrong in his attempt to get one marble of each color? Well, his first nine picks might yield five blue marbles and four white ones. But then the tenth marble would be red, and now he would have at least one of each color. The answer is 10.
填空题
Jordan has taken 5 math tests so far this semester. If he gets a 70 on his next test, it will lower the average (arithmetic mean) of his test scores by 4 points. What is his average now?
