Question

Evaluate 9 C 5. 24 3,024 45 126

Answer 1

Apply the formula of n!/{(r!)(n-r)!}


Where n= 9
And r= 5

9!/{(5!)(9-5)!}
= 9!/{(5!)(4)!}
= ( 9×8×7×6×5×4×3×2×1)/(5×4×3×2×1) (4×3×2×1)
= 126.

So, option d is correct.

Answer 2

A quics way to do this :-

9C5    = 9*8*7*6*5              3 * 7 * 6   =    126
             -------------        =     
              5*4*3*2*1