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NSWMaths Extension 1Combinatorics (ME-A1)

Quick questions on The multiplication principle and ordered selections: counting in stages, n^r with repetition, nPr without repetition, and restriction techniques

1short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is ordered selections WITH repetition?
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Now narrow to the most common kind of staged choice: you build an ordered arrangement of rr positions, and at every position you may pick any of the same nn objects, repeats allowed. Because choosing an object never removes it from the pool, every one of the rr boxes keeps all nn choices, and the multiplication principle gives

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