WAEC - Further Mathematics (2022 - No. 23)
In how many ways can six persons be paired?
5
10
15
20
คำอธิบาย
6C\(_2 = \frac{6!}{[6-2]![2!]}\)
\(\frac{6*5*4!}{4!*2!}\)
= \(\frac{6*5}{2}\)
= 15
6C\(_2 = \frac{6!}{[6-2]![2!]}\)
\(\frac{6*5*4!}{4!*2!}\)
= \(\frac{6*5}{2}\)
= 15