标题: 做PREP时遇到的数学难题,请牛人指教! [打印本页] 作者: Lyssazhao 时间: 2011-3-2 11:26 标题: 做PREP时遇到的数学难题,请牛人指教! 1、The rate of a certain chemical reaction is directly proportaional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100%, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?
2、Each of the students in a certain class received a single grade of P,F or I. What percent of the students in the class were females?
(1) of those who received a P, 40% were females. (2) of those who received either an F or I, 80% were males.
正确答案:E
3、Each employee of Company Z is an employee of either Division X or Division Y, but not both. If each division has some part-time employees, is the retio of the number of full-time employees to the number of part-time employees greater for Division X than for Company Z?
(1) The ratio of the number of full-time employees to the number of part-time employees is less for Division X than for Company Z. (2) More than half of the full-time employees of Company Z are comployees of Division X, and more than half of the part-time employees of Company Z are employees of Division Y.
正确答案:D
4、If x,y,z are integers greater than 1, what is the value of x+y+z? (1) xyz = 70 (2) x / yz = 7/ 10
正确答案:A作者: sdcar2010 时间: 2011-3-2 11:36
1、The rate of a certain chemical reaction is directly proportaional to the square of the concentration of chemical A present and inversely proportional to the concentration of chemical B present. If the concentration of chemical B is increased by 100%, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?
Rate = [A]*[A]/[B]
So [A]*[A]/[B] = [x*A]*[x*A]/[2B]
x*x = 2
x = 1.414
So A increases around 40%作者: sdcar2010 时间: 2011-3-2 11:40
2、Each of the students in a certain class received a single grade of P,F or I. What percent of the students in the class were females?
(1) of those who received a P, 40% were females. (2) of those who received either an F or I, 80% were males.
(1) 70=7*5*2作者: sdcar2010 时间: 2011-3-2 12:06
3、Each employee of Company Z is an employee of either Division X or Division Y, but not both. If each division has some part-time employees, is the retio of the number of full-time employees to the number of part-time employees greater for Division X than for Company Z?
(1) The ratio of the number of full-time employees to the number of part-time employees is less for Division X than for Company Z. (2) More than half of the full-time employees of Company Z are comployees of Division X, and more than half of the part-time employees of Company Z are employees of Division Y.