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Source: — Problem Solving |
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by Testluv » Thu Dec 02, 2010 12:13 am
Hi,

draw out the #s with spaces or "slots" between each of them. Then we have 10 slots. We also have a slot immediately before and immediately after the string of #s. We can place the 8 *s in any of these 12 slots. All the ways of placing 8 things into 12 spaces is the same as all the ways of "pulling out" 8 objects from 12. Thus, the answer is 12C8 (or 12C4).
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