1994 AMC 8 第 22 题
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所有题目均经美国数学协会（MAA）官方合法授权使用。
22.
右图中的两个转盘各转一次，并把得到的两个数相加。两个数之和为偶数的概率是
The two wheels shown at the right are spun and the two resulting numbers are added. The probability that the sum of the two numbers is even is
小提示：
第一个转盘中 占一半， 和 各占四分之一；第二个转盘被平均分成三份
On the first wheel covers half and and each cover a quarter; the second wheel is divided into equal thirds
大提示：
和为偶数当且仅当两个数同为偶数或同为奇数
The sum is even when both numbers are even or both are odd
解答：
第一个转盘中，，，。第二个转盘中，、、 各自的概率为 。
和为偶数需要两个数同奇偶。两数都为奇数时，第一个数是 或 ，概率为 ；第二个数是 ，概率为 ，所以概率为 。两数都为偶数时，第一个数是 ，概率为 ；第二个数是 或 ，概率为 ，所以概率为 。
总概率是 。
所以正确答案是 D。
On the first wheel, and On the second wheel, each of has probability
The sum is even when both numbers are odd or both are even. Both odd: the first is or and the second is giving Both even: the first is and the second is or giving
The total probability is
Thus, the correct answer is D .
其他年份的第 22 题
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