In a corporation, 50 percent of the male employees and 40percent of the female employees are at least 35 years old. If 42 percent of all the employees are atleast 35 years old, what fraction of the employees in the corporation arefemales?

  A. 3/5

  B. 2/3

  C. 3/4

  D. 4/5

  E. 5/6




  男a女b, 0.5a+0.4b=0.42(a+b);得b=4a,b/(a+b)=4/5.

  There are 11 women and 9 men ina certain club. If the club is to selecta committee of 2 women and 2 men, how many different such committees arepossible?

  A. 120

  B. 720

  C. 1,060

  D. 1,520

  E. 1,980




  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.



  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.