Respuesta :
The formula [tex]C(n, r)= \frac{n!}{r!(n-r)!} [/tex], where r! is 1*2*3*...r
is the formula which gives us the total number of ways of forming groups of r objects out of n objects.
for example, given 10 objects, there are C(10,6) ways of forming groups of 6, out of the 10 objects.
Thus, there are C(6, 3) many ways of forming different triples out of 6.
[tex]C(6, 3)= \frac{6!}{3!(6-3)!}=\frac{6!}{3!3!}=\frac{6\cdot5\cdot4\cdot3!}{3!3!}=\frac{6\cdot5\cdot4}{3!}=\frac{6\cdot5\cdot4}{3\cdot2\cdot1}=5\cdot4=20[/tex]
Answer: A.20
