Sure. First the formula : nPk = n!/(n-k)!. I assume you already knew that but it bears repeating.
So 11P4 = 11!/7! = 11 x 10 x 9 x 8
And one has to use permutations instead of combinations because (as explained earlier), even if the same alphabets are picked (say A, B, C) they can be arranged in different ways. Ie whenever "order" matters, use permutations.
HTH.
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Originally Posted by jatinet
rd_eastbay, 11P4 I know how to solve combinations but not sure of permutations will appreciate if you could explain a bit about solving such permutaions
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