【正确答案】 A

【答案解析】Since the average savings of the 10 students is $60, the total amount they have saved is $600 [TACTIC E1 ]. John has $130 and 3 students have none at all. If 5 other students have a total of $125 ($25 each, the least possible), then the tenth student will have $600 -$130 -$125 = $345. Column A is greater.

【正确答案】 B

【答案解析】Column A: since b ＜ 2, ab＜2a.
Column B: since b ＞ a, b + a ＞ a + a = 2a.
Column B is greater.
**Use TACTIC 1, Chapter 12. Plug in numbers that satisfy the condition.
Column A: (1.1)(1.8) = 1.98.
Colunm B: 1.1 + 1.8 = 2.9.
This time, Column B is greater. Eliminate Choices A and C, and try other numbers. Each time Column B will be greater. Choose B.