1984 AHSME Problems/Problem 19
Problem
A box contains balls, numbered . If balls are drawn simultaneously at random, what is the probability that the sum of the numbers on the balls drawn is odd?
Solution
There are exactly ways the sum can be odd: exactly are odd, exactly are odd, or exactly is odd. There are exactly odd numbers in the set. For the first case, there are possibilities. For the second case, there are possibilities. For the third case, there are possibilities. In each case, we're choosing out of the odd numbers which ones will be picked, and multiplying that by out of the even numbers, which one of those will be picked so that there are numbers. In total,there are desirable possibilities out of a total of possibilities. Thus, the answer is .
See Also
1984 AHSME (Problems • Answer Key • Resources) | ||
Preceded by Problem 18 |
Followed by Problem 20 | |
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