prep gwd 数学问题大集合~~~~

lissyUID: 2309016

还有3天考试了，突然发现还有几个数学不会，求教了~

1.  70 75 80 85 90 105 105 130 130 130
     标准差是22.4
     how many are more than 1 dv(标准差） below the mean of the numbers above?

这个关于标准差我只会算，这样提问我都没明白。

2.in the fraction x/y,x>0 and y>0,both integers,y=?
   (1) least common denominator of x/y and 1/y is 6
   (2) x=1

3.a certain quantity is measureed on two scales,the R-scales and the S-scales,that related linearly. measurement on the R of 6 and 24 correspond to measurement on the S of 30 and 60.what measurements on the R correspond to a measurement of 100 on the S?
(the answer is 48 ,why?)

4.six cards numbered from 1 to 6 are placed in a bowl.first one card is drawn and then put back into the bowl;then 2nd card is drawn.if the cards are drawns at random and if the sum of the numbers on the card is 8.what is the probility that on of cards drawn is 5?
(the answers is 2/5,but i think it must be 1/3)????

5.a certain characteristic in a large group has a distribution that is symetric about the mean m.if 68%of the distribution lies within one standard deviation d of the mean,what percent of the ditribution is less than m+d?
A.16% B.32% C.48% D.84% E.92%    the answer is D

6.is the integer n odd?
(1) n is divisible by 3
(2) 2n is divisible by twice as many positive integer as n.
还是没明白条件2什么意思，不就是说2n被2n整除吗？？？？

还有一个非常弱智的问题，1处以3有余数吗？是2吗？？？？