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Can somebody please provide some easy to remember mnemonic, such as PEMDAS, for GRE math counting questions. I can never get straight which formula to use depending on where order matters or order doesn't matter. I've recently started using mygretutor at www.mygretutor.com and here's the question that I am stumped on. I understand the solution after I see the answer, but I didn't even know where to start If an unbiased coin is tossed five times, then what is the probability of throwing three heads and two tails in any order? How does "in any order" change this question if order was important? The solution on mygretutor suggests to enumerate all possibilities, but is that feasible if there are many options?
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I am studying for my GREs and I came across a Counting Problem in the MGMAT Word Translations Guide that I am having difficulty solving. The question is: Gordon buys 5 dolls for his 5 nieces. The gifts include two identical Sun-and-Fun beach dolls, one Elegant Eddie dress-up doll, one G.I. Josie army doll, and one Tulip Troll doll. If the youngest niece does not want the G.I. Josie doll, in how many different ways can he give the gifts? My initial approach was to do the # of ways to ignore the rule: 2 x 1 [sun-fun dolls] x 3 x 2 x 1 = 12. Number of ways to break the rule: 2 x 1 [sun-fun dolls] x 2 x 1 x 1 = 4. Subtracting the # of ways to break the rule from # way to ignore the rule = 12 - 4 = 8. This is not correct though.