单选题One hour after Tom started walking from X to Y, a distance of 45 miles. Bob started walking along the same road from Y to X. If Tom’s walking rate was 3 miles per hour and Bob’s was 4 miles per hour,
单选题Five integers between 10 and 99，inclusive，are to be formed by using each of the ten digits exactly once in such a way that the sum of the five integers is as small as possible．What is the greatest pos
单选题If rs=s, what is the value of r+s?1r=425=0
单选题有7个数字：a，a，b，b，c，c，d，从中任取两个，问这两个数字相同的概率?
单选题下面哪一个不可能为多少天的小时数目?
单选题X和Y是从集合{1，2，3，4，5，6}中随机挑选出来的不相等的两个数，问在所有的和中，X+Y是完全平方数的概率?
单选题0到9这10个数字能够组成多少个没有重复数字的三位数?
单选题数列按照1，2，2，3，3，3，4，4，4，4，5，…的规律一直排下去，which of the following is the 100th number?
单选题Despite legislation designed to stem the
单选题If three water pipes A, B and C are working at the same time, they can fill a swimming pool in 6 hours, if only A and B work, it needs 8 hours to fill the swimming pool, in how many hours can C fill t
单选题When opened and lying flat, a birthday card is in the shape of a regular hexagon. The card must be folded in half along 1 of its diagonals before being placed in an envelope for mailing. Assuming that
单选题What is the sum of 3 consecutive integers? 1 The sum of the 3 integers is less than the greatest of the 3 integers。 2 Of the 3 integers，the ratio of the least to the greatest is 3．
单选题Each of the balls in a bag is red, or green, or blue. If one ball is to be removed at random, what’s the probability that the ball will be green?1There are 5 red balls and 4 blue balls in the bag.2The
单选题Given a positive number N, when N is rounded by a certain method for convenience, call it Method Y, the result is 10" if and only if n is an integer and 5×10n-1≤N5x10n. In a certain gas sample, there
单选题The annual stockholders’ report for Corporation X stated that profits were up 10 percent over the previous year，although profits as a percent of sales were down 10 percent．Total sales for that year we
单选题3×104 is greater than 4×103 by what percent?