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OG 11- Quant Sample- Question 11 [#permalink]
19 Mar 2007, 16:10
Would anybody have a formula/explanation for this:
"Of the three-digit integers greater than 700, how many have two digits that are equal to each other and the remaining digit different from the other two?"
Could you explain this more? I am not sure to get it
8xx where x = 0~7, 9 - 9 of them 8x8 where x = 0~7, 9 - 9 of them 88x where x = 0~7, 9 - 9 of them
8xx where x = 0~7, 9 - 9 of them -> Keep the 8 fixed and make the ten's and unit's digits the same. For example, 800, 811, 822, etc. However, you cannot have 8xx where x = 8 since then, there would be 3 (not 2) identical numbers.
8x8 where x = 0~7, 9 - 9 of them -> Keep the hundred's and unit's digits fixed and rotate the middle digits.
88x where x = 0~7, 9 - 9 of them -> Keep the first two digits fixed and rotate the last digits.