Quant Question about Set and Combination

GRE Quant Problem Solving
1

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Hi All,

Could someone please clarify why we have to use the combination in this case? I used permutation because I thought using combination would have double-counted some numbers. so using combination, would that mean for example: {1,2,3,4} is counted and so is {4,3,2,1,}, and {2,3,4,1) to so and so forth…

THank you!

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Actually you’re describing permutation, where “{1,2,3,4} is counted and so is {4,3,2,1,}, and {2,3,4,1) to so and so forth”. Combination is the case where the order does not matter.