快考试~~竟然有这么都prep不会 请大家帮忙啊~~

小纾

1.A certain jar contains only b black marbles, w white marbles and r red marbles. If one marble is to be chosen at random from the jar, is the probability that the marble chosen will be red greater than the probability that the marble chosen will be white?
1)r/(b+w)>w/(b+r)
2)b-w>r

2.If x and y are positive integers, is xy  a multiple of 8?
1) the greast common divisor of x and y is 10
2)the least common multiple of x and y is 100

3.what is the gresastest possible area of a triangular region with one vertex at the center of acircle of radius 1 and the other two vertices on the circle
我怎么算都是4分之根号3

SkinsRe

A 把条件1化简,得出r<w,条件2不确定
C 条件1,x=10,y=10,条件2,x=4,y=25
1/2吧

小纾

谢谢了了~~可是1的式子怎么化简啊 好白痴的问题~~