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maths MC !! help urgent

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HELP ME THE FOLLOWING MC: http://blog.yahoo.com/_FSL2RCBLLRU5CBY6F5S27EUMAE/articles/1072572/index 更新: 回答者: cf ( 小學級 5 級 ) what means C in no 26?

最佳解答:

26) The answer is C The required probability =(12C1*40C1+12C2)/(52C2) =7/17 32) The answer is C By using triangle inequality, AC+BC>AB 4x+(3x-2)>8 7x>10 x>10/7 When x=6 AC=4x=4*6=24 BC+AB=(3*8-2)+8=24 By using triangle inequality, BC+AB>AC However, in this case, BC+AB=AC, which is impossible Therefore x<6 and x>10/7 i.e. 10/7=2 and x<2 Two areas do not overlap i.e. no solution In the graph of x>=-2 and x<=-3 Two areas do not overlap i.e. no solution In the graph of x>=6 and x=<7 Two areas do overlap i.e. 6==1 III is correct since the shaded region lies above 6x-y=20 Thus, it is 6x-y>=20 2013-06-18 14:00:07 補充: C in no.26 and 39 mean "combination" instead of "choose". In your calculator, u need to press the buttom in the way as follow: [(][1][2][shift][÷][1][X][4][0][shift][÷][1][+][1][2][shift][÷][2][)][÷][(][5][2][shift][÷][2][)] 2013-06-18 14:00:16 補充: In order to have the symbol "C", u need to press [shift][÷] I think the use of combination will be taught in F.5 Chapter 4 and 5.

其他解答:

if you do not learn about C, you can try this. the required probability =P(1 face and 1 other) + P(2 faces) =2(3/13)(40/51) + (3/13)(11/51) =7/17
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