Tennisboy

275、        point X is randomly drawn inside a rectangle ABCD, what's the value of XA2(square)?
XC2(square)-XB2+XD2
XB2+XD2-XC2
XD2+XC2-XB2
XB2+XC2-XD2
quote:XA,XB,XC,XD are the lengths of their respective segments

276、        还考了一道貌似狗狗上么有的，我找到了一道prep上面类似的题
A vending machine is designed to dispense 8 ounces of coffee into a cup.After a test that recorded the number of ounces of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in ounces, were selected from the data.If the 1,000 recorded amounts have a mean of 8.1 ounces and a standard deviation of 0.3 ounce, how many of the 12 listed amounts are within 1.5 standard deviations of the mean?
(A) Four
(B) Six
(C) Nine
(D) Ten
(E) Eleven
概率论啊
题目给的12个数为 7.518.227.868.36
8.097.838.308.01
7.738.257.968.53
题目提供平均数为8.1标准偏差为0.3。为哪些数差1.5个标准偏差
所以 0.3*1.5=0.45
8.1+0.45= 8.55
8.1-0.45= 7.55 所以找落在7.55~8.55 的数即可。
哦哦，其实很简单啦，就是数数~
The answer is E.