Question

If $_n P_4 = 20 , _n P_3$, find $n$.

Answer 1

nP₄=20×nP₃          Value of n=?
=>n(n-1)(n-2)(n-3)=20.n(n-1)(n-2)             {n(n-1)(n-2) from both sides gets cancelled out}
=>(n-3)=20
=>n=17

therefore value of n is 17
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