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If $$^nP_r = ^nP_{r+1}$$ and $$^nC_r = ^nC_{r-1}$$, then the value of $$r$$ is equal to:
We have the two relations
$$^nP_r \;=\; ^nP_{\,r+1}\qquad\text{and}\qquad ^nC_r \;=\; ^nC_{\,r-1}.$$First we use the permutation formula
$$^nP_k \;=\; \frac{n!}{(n-k)!}.$$Substituting $$k=r$$ and $$k=r+1$$ we obtain
$$^nP_r \;=\; \frac{n!}{(n-r)!},\qquad ^nP_{\,r+1} \;=\; \frac{n!}{(n-r-1)!}.$$Since these two are equal, their quotient is $$1$$:
$$\frac{^nP_r}{^nP_{\,r+1}} \;=\; \frac{\dfrac{n!}{(n-r)!}}{\dfrac{n!}{(n-r-1)!}} \;=\; \frac{(n-r-1)!}{(n-r)!} \;=\; \frac{1}{n-r} \;=\; 1.$$Thus
$$n-r \;=\; 1\;\;\Longrightarrow\;\; r \;=\; n-1. \quad -(1)$$Next we use the combination formula
$$^nC_k \;=\; \frac{n!}{k!\,(n-k)!}.$$Putting $$k=r$$ and $$k=r-1$$ we get
$$^nC_r \;=\; \frac{n!}{r!\,(n-r)!},\qquad ^nC_{\,r-1} \;=\; \frac{n!}{(r-1)!\,(n-r+1)!}.$$Because these two are equal, their quotient is also $$1$$:
$$\frac{^nC_r}{^nC_{\,r-1}} \;=\; \frac{\dfrac{n!}{r!\,(n-r)!}} {\dfrac{n!}{(r-1)!\,(n-r+1)!}} \;=\; \frac{(r-1)!\,(n-r+1)!}{r!\,(n-r)!} \;=\; \frac{n-r+1}{r} \;=\; 1.$$Hence
$$n-r+1 \;=\; r \;\;\Longrightarrow\;\; n+1 \;=\; 2r \;\;\Longrightarrow\;\; r \;=\; \frac{n+1}{2}. \quad -(2)$$Now both (1) and (2) must hold simultaneously. Equating the two expressions for $$r$$ we write
$$n-1 \;=\; \frac{n+1}{2}.$$Multiplying by $$2$$ and simplifying, we have
$$2n-2 \;=\; n+1 \;\;\Longrightarrow\;\; n-3 \;=\; 0 \;\;\Longrightarrow\;\; n \;=\; 3.$$Finally, substituting $$n=3$$ into $$r=n-1$$ gives
$$r \;=\; 3-1 \;=\; 2.$$Therefore
$$r = 2.$$Hence, the correct answer is Option C.
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