標題:
Probability 27
發問:
When a market gardener takes n cuttings from a shrub and plants them, the number X that will root successfully is a discrete random variable with P(X = r) = 2r/n(n+1) , r = 1, 2, 3, ... , n . For n = 20 , find the probability that the gardener will make a loss. 更新: Ans: 1/14 更新 2: Continual part (may be useful) The total cost in dollar to the gardener of taking and planting n cuttings is equal to 20+0.8n^2 . Cuttings that root successfully are sold by the gardener of $60 each .
最佳解答:
Total cost of taking and planting 20 cuttings = 20 + 0.8 x 202 = 340 So there should be 6 cuttings rooted successfully to make a profit. In other words, if 5 or less cuttings rooted successfully, the gardener will make a loss. Hence, the probability that the gardener will make a loss is: Σ (r = 1 to 5) 2r/(20 x 21) = (1/210) Σ (r = 1 to 5) r = 15/210 = 1/14
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其他解答:
The total cost in dollar to the gardener of taking and planting n cuttings is equal to 20+0.8n^2 . Cuttings that root successfully are sold by the gardener of $60 each .|||||Does the question state under what condition will the gardener make a loss ?63D0B758E2D502CC
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