PP-T2-PS20

[smilego]

20. 2942-!-item-!-187;#058&003104
For any positive integer n, the length of n is defined as the number of prime factors whose product is n. For example, the length of 75 is 3, since 75 = 3 x5 x 5. How many two-digit positive integers have length 6 ?

(A) None
(B) One
(C) Two
(D) Three
(E) Four

答案是 (C)
這題我選 (B), 我只有 解出 64 有 長度6
另外一個數字 我求不出來
請問可以幫忙解一下嗎,謝謝!!

[nemolee]

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