再加JJ

GR 2003-01-12 21:05:48

看到老JJ就勾起回忆:

K=0.1-(0.1)^2 问x>0.05?
1) K>0.009/x
2) K<0.0009/x

我选D

K=0.1-(0.1)^2 =0.1-0.01=0.09
1) K>0.009/x
x>0.009/k=0.1

X>0.1>0.05 所以(1)足够

2) K<0.0009/x
x<0.0009/k
x<0.0009/0.09=0.01

x<0.01<0.05 所以(2)足够回答

ANS: D

2. 60 cars,either full size or midsize or compact. 10 are red, 19 are blue, How many cars are full size?

1) No red or blue cars are full size
2) The number of full size car is greater than the sum of mid size and compact cars

我选C

由以下表来表达

Fullsize, F midsize, M compact, C subtotal

White, W 31 0 0 31

Red, R 0 10

Blue, B 0 19

Subtotal 31 60

因 RF and BF =0 (given)

所以 M+C = or at least =10+19

由 1st row, F=<31

F+M+C=60

F must be either 30, or 31

题干给 F>M+C

所以 F 不能是 30, 只能是31, M+C= 29

3. 0.00625 is between 1/10^(n-1) and 1/10^n , waht is the value of n?

Ans: n=3

就是8 人中选4 人. 包括要选Andria不选Julia 的机率?

因为

P( 选4人选Andria不要JULIA)= P(ANDRIA)*P(NOTJuLIA)*P(NOTJuLIA)*P(NOTJuLIA)

=1/8 * (1-P(Julia) * [1-P(Julia) ] * [1-P(Julia) ] * [1-P(Julia) ]

=1/8 * [1-(1/7)] * [1-(1/6)] * [1-(1/5)]

=1/8 * 6/7 * 5/6 * 4/5

=1/14

如有不对请指教讨论

>>打印此页<<

>>关闭窗口<<