GWD-18 Q6. The function f is defined for each positive three-digit integer n by f(n) = 2^x3^y5^z, where w, y, and z are the hundreds, tens, and units digits of n, respectively. If m and v are three-digit positive integers such that f(m) = 9f(v), then m-v = ? Q13. Each of 20 parents chose one of five days from Monday through Friday to attend parent-teacher conferences. If more parents chose Monday than Tuesday, did at least one of the parents choose Friday? (1) None of the five days was chosen by more than 5 parents. (2) More parents chose Monday than Wednesday. Q18. A certain characteristic in a large population has a distribution that is symmetric about the mean m. If 68 percent of the distribution lies whinin one standard deviation d of the mean, what percent of the distribution is less than m+d ? Q23. The toll for crossing a certain bridge is $0.75 each crossing. Drivers who frequently use the bridge may instead purchase a sticker each month for $13.00 and then pay only $0.30 each crossing during that month. If a particular driver will cross the bridge twice on each of x days next month and will not cross the bridge on any other bridge on any other day, what is the least value of x for which this driver can save money by using the stickers? Q24. The positive numbers w,x,y,and z are such that x is 20 percent greater than y, y is 20 percent greater than z, and w is 20 percent less than x. What percent greater than z is w ? Q30. From May 1 to May 30 in the same year, the balance in a checking account increased. What was the balance in the checking account on May 30? (1) If, during this period of time, the increase in the balance in the checking account had been 12 percent, then the balance in the account on May 30 would have been $504. (2) During this period of time, the increase in the balance in the checking account was 8 percent. QX. If the probability is o.54 that Stock A will increase in value during the next month and the probalbility is 0.68 that Stock B will increase in value during the next month, what is the greatest possible value for the probability that neither of these two events will occur? 拜托大家了Orz 真的很谢谢你们Q_Q --

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