明天就考了，求教几道不懂数学的题目！

neversight · 发表于 2009-12-9 12:05:10

A shipment of 8 television sets contains 2 black-and-white sets and 6 colors sets. If 2 television sets are to be chosen at random from this shipment, what is the probability that at least 1 of the 2 sets chosen will be a black-and-white set? 答案是11/28
我算出来是13/28，能不能解释下思路阿？

The tens digit of positive integer X is 3. Is the units digit of X greater than 4? 1,The units digit of 2X is less than the units digit of X
2, The tens digit of 2X is 7 Answer:E 我选的D

Can a certain rectangular sheet of glass be positioned on a rectangular tabletop so that it covers the entire tabletop and its edges are parallel to the edges of the tabletop? 1,The tabletop is 36 inches wide by 60 inches long. 2,The area of one side of the sheet of glass is 2400 square inches. Answer: E 我选的C

During a 10-week summer vacation, was the average (arithmetic mean) number of books that Carolyn read per week greater than the average number of books that Jacob read per week? 1, Twice the average number of books that Carolyn read per week was greater than 5 less than twice the average number of books that Jacob read per week. 2, during the last 5 weeks of the vacation, Carolyn read a total of 3 books more than Jacob.
Answer: A 我选的E

neversight · 发表于 2009-12-9 12:10:02

请NN们帮帮我啊……

neversight · 发表于 2009-12-9 12:29:37

为什么没人理我？

roboty · 发表于 2009-12-9 12:41:49

It should be 13/28.

Probability that none of the TV will be B/W = 6C2 / 8C2 =15/28

So at least one TV will be B/W= 1-15/28 = 13/28

明天就考了，求教几道不懂数学的题目！

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