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標題:

F.6 Math&stat question

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發問:

There are 30 balls of which 10 balls are coloured. All the balls are put into a bag. A random sample of 10 balls are taken from the bag. Find the number of ways that the student can take the sample so that there are 3 coloured balls in the sample. Please explain also, thz

最佳解答:

Total number of balls = 30 In which 10 of them are coloured.For the sample of 10 balls, 3 of them are coloured. So, we have to take 3 coloured balls out of the ten coloured balls. Number of ways to take the coloured ball = 10C3 For the sample of 10 balls, 7 of them are non-coloured. So, we have to take 7 non-coloured balls out of the twenty coloured balls. Number of ways to take the coloured ball = 20C7 So, no. of ways to take the balls = 10C3 X 20C7 = 9 302 400

其他解答:E2A5F59BAA12C031