请教几道prep的题

Lavinia13

这几道题是刚刚在官方prep软件上做到的
1.Of the 1,400 college teachers surveyed, 42 percent said that they considered engaging in research an essential goal. How many of the college teachers surveyed were women?

(1) In the survey, 36 percent of the men and 50 percent of the women said that they considered engaging in research an essential goal.

(2) In the survey, 288 men said that they considered engaging in research an essential goal.

2.
If n and t are positive integers, what is the greatest prime factor of the product nt?
1) the greatest common of n and t is 5
2) the least common multiple of n and t is 150
2这个条件我不是很懂，最小公约数的话万一被约掉了一个很大质因数呢？


3.
If p is a positive odd interger, what is the remainder when p is divided by 4?
1) When p is divided by 8, the remainder is 5
2) p is the sum of the squres of two positive integer.
这道题我对2这个条件不是很懂，希望有大神解答一下

4.
During an experiment, some water was removed from each of 6 water tanks. If the standard deviation of the volumes of water in the tanks at the begnning of the experiment was 10 gallons, what was the standard deviation of the volumes of water in the tanks at the end of the experiment?
1) For each tank, 30 percent of the volume of water that was in the tank at the beginning of the experiment was removed during the experiment.
1) The average volume in the tanks at the end of the experiment was 63
这道题我觉得任何一个条件都推不出啊




希望有大神能帮我解答一下，万分感谢~