AMC 8 1989 Problem 16
AMC8 1989 年第 16 题
奇偶性★★★☆☆
In how many ways can 47 be written as the sum of two primes?
有多少种方式可以将 47 写成两个质数之和？
- A.0
- B.1
- C.2
- D.3
- E. / 多于 3
正确答案 · Correct Answer
A
解析 · Solution
Solution 1
Since 47 is odd, if two integers sum to 47, then one is odd while the other is even. The even number must be 2 as there are no other even prime numbers. But this would require the odd number to be 47 - 2 = 45, which is not prime. Therefore, there 0 ways to write 47 as the sum of two primes.
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