AMC8 1994

AMC8 1994 · Q22

AMC8 1994 · Q22. It mainly tests Probability (basic), Parity (odd/even).

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

右侧所示的两个轮子被转动，得到两个数字相加。两个数字之和为偶数的概率是

(A) $\frac{1}{6}$ $\frac{1}{6}$

(B) $\frac{1}{4}$ $\frac{1}{4}$

(D) $\frac{5}{12}$ $\frac{5}{12}$

(E) $\frac{4}{9}$ $\frac{4}{9}$

Answer

Correct choice: (D)

正确答案：（D）

Solution

Even sum: both even or both odd. P(odd1)*P(odd2) + P(even1)*P(even2) = (3/4)(1/3) + (1/4)(2/3) = 1/4 + 1/6 = 5/12.

偶数和：两个都是偶数或两个都是奇数。P(奇1)*P(奇2) + P(偶1)*P(偶2) = (3/4)(1/3) + (1/4)(2/3) = 1/4 + 1/6 = 5/12。

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