作者currycurry (古錐仔)
看板GMAT
標題[問題] OG-11th-Diagnostic Test-DS #25
時間Mon May 5 00:04:08 2008
If the units digit of integer n is greater than 2, what is the units digit
of n?
(1) The units digit of n is the same as the units digit of n^2.
(2) The units digit of n is the same as the units digit of n^3.
答案是 (E) both statements together are still not sufficient.
想問的是：
OG解釋中的(2)：
Once again, 5 and 6 are the only numbers which, when cubed, will both have
a 5 or 6 respectively in their units digit.
個人認為，應該還有 4 及 9，也符合三次方之後，個位數仍相同的條件
是否有人有相同看法？
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◆ From: 140.116.138.235
※ 編輯: currycurry 來自: 140.116.138.235 (05/05 00:06)
1F：推 Engedi:OG的意思是說 將(1)(2)條件都考慮 也只能得出5 or 6的答案 05/05 00:11
2F：→ Engedi:未知數算出來不是唯一解就視為條件不足 妳想的4or9 也同理 05/05 00:12
3F：→ currycurry:感謝,答案是瞭解，但單獨對(2)的說明，認為應包含4,9 05/05 12:43