GMATPrep错误题目请教

ripplewan · 发表于 2006-7-15 22:56:00

A company plans to assign identification numbers to its employees. Each number is to consist of four different digits from 0 to 9, inclusive, except that the first digit cannot be 0. How many different identification numbers are possible?
Answer: 4536
But I think, C(9,1)C(9,1)C(8,1)C(7,1).Where am I wrong?

beibeideng · 发表于 2006-7-15 23:12:00

应该这样

P(10, 4)-P(9,3)

kallyli · 发表于 2006-7-15 23:14:00

you're right, just calculate carefully

beibeideng · 发表于 2006-7-15 23:16:00

C(9,1)C(9,1)C(8,1)C(7,1)IS EQUAL TO 4536

GMATPrep错误题目请教

GMATPrep错误题目请教

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