Directions: In the following of the questions,choose the best answer from the five choicew listed.

单选题 What is the measure of the angle formed by the minute and hour hands of a clock at 1:50? (1) 90° (B) 95° (C)105° (D) 115° (E) 120°

【正确答案】 D

【答案解析】For problems such as this, always draw a diagram. The measure of each of the 12 central angles from one number to the next on the clock is 30°. At 1:50 the minute hand is pointing at 10, and the hour hand has gone

of the way from 1 to 2. Then, from 10 to 1 on the clock is 90°, and from 1 to the hour hand is

(30)°= 25°, a + 25° = 115°.

单选题 Which of the following CANNOT be expressed as the sum of three consecutive integers?

A、 (A) 18
B、 (B) 24
C、 (C) 28
D、 (D) 33
E、 (E) 36

【正确答案】 C

【答案解析】The sum of three consecutive integers can be expressed as n+(n+1)+(n+2)=3n+3=3(n+1), and so must be a multiple of 3. Only 28, Choice C, is not a multiple of 3. **Quickly add up sets of three consecutive integers: 4 + 5 + 6 = 15, 5 + 6 + 7 = 18, 6 + 7 + 8 = 21, and so on, and see the pattern (they're all multiples of 3); or cross off the choices as you come to them.

单选题 Sandrine is now 5 times as old as Nicholas, but 7 years from now, she will be 3 times as old as he will be then. How old is Sandrine now?

A、 (A) 15
B、 (B) 20
C、 (C) 21
D、 (D) 25
E、 (E) 35

【正确答案】 E

【答案解析】
Set up a table.

Time	Nicholas	Sandrine
Now	x	5x
In 7 years	x+7	5x+7

Then
5x + 7 = 3(x + 7)

5x + 7 = 3x + 21

2x=14