Math Olympiad For Primary School » grade 9 http://mathandflash.com Problem Solving Math Olympiad For Primary School Fri, 18 May 2012 03:44:19 +0000 en hourly 1 http://wordpress.org/?v=3.3.2 Math For Grade 12 (High School) http://mathandflash.com/math-for-grade-12-high-school/ http://mathandflash.com/math-for-grade-12-high-school/#comments Wed, 25 Nov 2009 04:35:53 +0000 admin http://mathandflash.com/?p=362 Starting this time maybe I should update on the discussion questions the national exam, because the national examination (UN) High School only a few months away. Come and join to be a member on this blog.

Problem this week:
In a box of there are 7 red and 5 white marbles. Three marbles was taken from a box with random. The opportunities/odds of least 1 white marbles taken from a box is ….

Get this answer ?

Answer:
The discussion about the chances for above:
Total marbles =12. Taken 3, it  means that the sample space is 12C3.

We can conclude that at least 1 white means: 2 white 1 red, 1 white 2 red and 3 white (all white). So the odds: the number of possibilities / sample space.

Odds = (5C1.7C2 +5 C2.7C1 +5 C3.7C0) / 12C3

Why 5C1.7C2 ? It taken 3 balls, 1 white, 2 red. Total’s 5 white ball, red ball trus’s total 7.

I hope, you can count it self to get the result.

C is a combination. For those who forgot, please check again notes. Obviously not clearly yes please give comments on this blog.

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