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If npr =1320 and ncr=220 then find n

Answer» N!/(n-R)!=1320,n!/r!(n-r)!=220
on DIVIDING ,r!=6
3×2×1=r!=3!
r=3
n!/(n-r)!=1320
n!/(n-3)!=1320
n(n-1)(n-2)(n-3)!/(n-3)!=1320
n(n-1)(n-2)=1320
12×11×10=1320
so n=12


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