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题库 / Prep2007E1-DS-142
If x is a positive integer, what is the least common multiple of x, 6, and 9 ?
(1) The least common multiple of x and 6 is 30.
(2) The least common multiple of x and 9 is 45.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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（1）最小公倍数30=2x3x5, 说明了x为5的倍数以及小于30，以及由于2是一次方以及5也是一次方，所以x不能是20，也不会是25，所以只能是5/10/15, 带回去题干最小公倍数都是90。还有另外一种做法就是x和6的LCM=30,那题干中的9和30都有公约数3， 所以9的3会跟x和6一起被3公除，那9/3=3, 3*30=90.
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