List Tconsists of 30 positive decimals, none of which is an integer, and the sum of the 30 decimals is S.The estimated sum of the 30 decimals, E, is defined as follows. Each decimal in T whose tenths digit is even is rounded up to the nearest integer, and each decimal in Twhose tenths digit is odd is rounded down to the nearest integer; E is the sum of the resulting integers. If -Iof the decimals in Thave a tenths digit that is even, which of the following is a possible value of E- S?
I. -16
II. 6
III. 10
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only
(E) I, II, and III
答案：B
Is the sum of the integers x and y a prime number?
(1) x is an even prime number.
(2) y is a prime number between10 and 20.
A. Statement (1) ALONE is sufficient, but statement(2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement(1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient,but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOTsufficient.
参考答案：E
题目翻译：x和y的和是不是质数?
题目全解：(1)2 is the only prime even number. We don't know what Y is. Insufficient;
(2)Y can be 11,13,... We don't know what X is. Insufficient;
Together,2+11 = 13 Prime; 2+13 = 15 not Prime. Insufficient.
Hence E.
Each signal that a certain ship can make is comprised of 3different flags hanging vertically in a particular order. How many unique signals can be made by using4 different flags?
A. 10
B. 12
C. 20
D. 24
E. 36
参考答案：D
题目翻译：4个不同的旗，三个能组成一个新信号。求不同信号数量。
题目全解：4个中选出3个排列，C(3,4)*P(3,3)= 24
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