1.

C ( 2 n , 3 ) : C ( n , 3 ) = 12 : 1

Answer»

²ⁿC₃ : ⁿC₂ = 12 : 1

use the concept, ⁿCₐ =n!/a!(n-a)!

2n(2n-1)(2n-2)(2n-3)!/3!(2n-3)! : n(n-1)(n-2)!/2!(n-2)! = 12 : 1

{2n(2n -1)(2n-1)/6}/{n(n-1)/2} = 12/1

{4n(2n-1)(n-1)}/3{n(n-1)}=12

4(2n-1)/3 = 12

2n - 1 = 9

2n = 10

n = 5



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