单选题在一次宴会上一共有12个人，如果每个人和其他的人各握手一次，那么一共有多少次握手?
单选题Is x less than y ?1 x-y+102 x-y-l0
单选题The rate at which a road wears depends on
单选题在一个有n个数的序列中，数15比序列的median少了1.5个deviation，数22比median多了2个deviation，求这个序列的median。
单选题Machines X and Y run at different constant rates，and machine X can complete a certain job in 9 hours． Machine X worked on the job alone for the first 3 hours and the two machines，working together，then
单选题The chemical adenosine is released by brain
单选题There are five positive numbers n+2, n+1, n-2, n and n+9, which of the following could be the difference between the mean and the median?
单选题A bank account earned 2% annual interest, compounded daily, for as long as the balance was under $1,000, starting when the account was opened. Once the balance reached $1,000, the account earned 2. 5%
单选题If an integer n is divisible by both 12 and 15, it must also be divisible by which of the following?
单选题State X has a sales tax rate of k percent on all purchases and State Y has a sales tax rate of n percent on all purchases. What is the value of k - n ?1 The sales tax on a $15 purchase is 30 cents mor
单选题If x is an even integer, which of the following is an odd integer?
单选题Which of the following is the coefficient of xy in3x+4y-xy4x+3y+1?
单选题Archaeologists working in the Andes Mountains
单选题A certain mathematical operation may be represented by the symbol@. For all nonzero a and b, does a@b=b@a?1m@n=12, for all nonzero m.2a@6=aba2+b2, for all nonzero a and b.
单选题Each of the five divisions of a certain company sent representatives to a conference. If the numbers of representatives sent by four of the divisions were 3, 4, 5, and 5, was the range of the numbers
单选题Khalil drove 120 kilometers in a certain amount of time. What was his average speed, in kilometers per hour, during this time?1 If Khalil had driven at an average speed that was 5 kilometers per hour
单选题If x and y are integers, is xy + 1 divisible by 3 ?1 When x is divided by 3, the remainder is 1. 2 When y is divided by 9, the remainder is 8.
单选题在某个数列中，从a1开始每一项都比前一项多x，a1=12，a41=92，问x的值为多少?