求助，GWD题，拜托各位了，谢谢。

lord6666

1.A positive integer n is said to be "prime-saturated" if the product of all the different positive prime factors of n is less than the square root of n. What is the greatest two - digit prime-saturated integer?
A.99 B.98 C.97 D.96E.95
answer is D. why?

A photographer will arrange 6 people of 6 different heights for photograph by placing them in two rows of three so that each person in the first row is standing in front of someone in the second row. The heights of the people within each row must increase from left to right, and each person in the second row must be taller than the person standing in front of him or her. How many such arrangements of the 6 people are possible?
A.4 b.6 c.9 d.24 e.36
answer is a, why?

A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow. If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?
a.3/64 b.1/20 c.1/16 d.1/12 e. 1/8
answer is b, why?

Running at their respective constant rates, machine X takes 2 days to produce w widgets than machine Y. At these rates, if the two machines together produce 5/4 w widgets in 3 days. How many days would it take machine X alone to produce 2w widgets?
a.4 b.6 c. 8 d. 10 e. 12
answer is e,why?

In a corpotation,50 percent of male employees and 40 percent of female employees are at least 35 years old. If 42 percent of all the employees are at least 35 years old, what fraction of the employees in the corporation are female?
a.3/5 b. 2/3 c.3/4 d.4/5 e.5/6
answer is d,why?

If 10的50次方减74 is written as an integer is base 10 notation, what is the sum of the digits in that integer?
a.424 b.433 c.440 d.449 e.467
answer is c, why?