求教几道GWD-1·的数学题啊！都是概率的题目~

brendawan

由于数学是在是太差了，概率题目觉得好难啊！今天第一次做GWD数学居然错了11个！几道概率题基本全军覆没，所以求各位牛人看看~
Q2:
A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster.  If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?

A.    0
B.    1/9
C.    2/9
D.    1/3
E.    1
Answer:
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Q9:
A gardener is going to plant 2 red rosebushes and 2 white rosebushes.  If the gardener is to select each of the bushes at random, one at a time, and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?

A.    1/12
B.    1/6
C.    1/5
D.    1/3
E.    1/2
Answer:
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Q17:
In Town X, 64 percent of the population are employed, and 48 percent of the population are employed males.  What percent of the employed people in Town X are females?

A.    16%
B.    25%
C.    32%
D.    40%
E.    52%
Answer:
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Q37:
A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow.  If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?

A.    3/64
B.    1/20
C.    1/16
D.    1/12
E.    1/8
Answer:
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tian20111

Q2
每辆车都骑过的方案相当于把三辆车排序 有3*2*1种 总共方案就是3*3*3种 概率即
P=(3*2*1)/3^3=2/9
Q9
给四种植物标上红1 红2 白1 白2 总共排列方式4*3*2*1种 二红在中间相当于红的和白的内部排序 即(2*1)*(2*1) 概率即
P=[(2*1)*(2*1)]/(4*3*2*1)=1/6
Q17
48%是employeed males 那么52%是employeed females+unemployeed people 又unemployeed people占总人口的(1-64%)=36% 所以employeed females占总人口的16% 再16%/48%=1/3
Q37
第一次抽到红的的概率是4/16 第二次抽到蓝的的概率是3/15 概率即
(4/16)*(3/15)=1/20

xxpatzz

Q17 应该是 16%/64% = 25% 得到 employed female / total employed

brendawan

Q2
每辆车都骑过的方案相当于把三辆车排序 有3*2*1种 总共方案就是3*3*3种 概率即
P=(3*2*1)/3^3=2/9
Q9
给四种植物标上红1 红2 白1 白2 总共排列方式4*3*2*1种 二红在中间相当于红的和白的内部排序 即(2*1)*(2*1) 概率即
P=[(2*1)*(2*1)]/(4*3*2*1)=1/6
Q17
48%是employeed males 那么52%是employeed females+unemployeed people 又unemployeed people占总人口的(1-64%)=36% 所以employeed females占总人口的16% 再16%/48%=1/3
Q37
第一次抽到红的的概率是4/16 第二次抽到蓝的的概率是3/15 概率即
(4/16)*(3/15)=1/20

-- by 会员 tian20111 (2011/6/18 0:26:38)

果然是牛牛啊！醍醐灌顶啊！！我觉得第二题真的很难啊！想了一阵子才弄明白的~汗！我实在太弱了！

brendawan

Q17 应该是 16%/64% = 25% 得到 employed female / total employed

-- by 会员 xxpatzz (2011/6/18 1:26:03)

谢谢啊！