document.write( "Question 1173585: Kate wants to choose 3 out 13 different items as the christmas presents. Given that 4 items are from shop B, and 3 items from shop C, find the number of combinations in each of the following cases.
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Algebra.Com's Answer #798879 by ewatrrr(24785) $\"\"$ $\"About$

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document.write( "Hi,
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document.write( "13 Items:  6 ShopA   4 ShopB     3 ShopC
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document.write( "Choosing 3, find the number of combinations in each of the following cases.
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document.write( "nCr = (n!)/(r!(n - r)!).   nCr on Your Caclulator
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document.write( "A. Choosing 3   items from the same shop: 6C3 + 4C3 + 3C3 =   20+4+1 = 25
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document.write( "B. Choosing 3 items which are not from shop A:  7C3 = 35
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document.write( "C. Choosing at least 1 item from shop A:  
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document.write( "  (6C1)(7C2) + (6C2)(7C1) + (6C3) = (6)(21) + (15)(7) + (20)
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document.write( "Wish You the Best in your Studies.
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