JAMB - Mathematics (2004 - No. 19)
In how many ways can 2 students be selected from a group of 5 students in a debating competition?
25 ways
10 ways
15 ways
20 ways
คำอธิบาย
The number of ways of selecting the debtors = \(^5C_2\) ways
\(^5C_2\) = \(\frac{5!}{(5 - 2)!2!}\)
= \(\frac{5 . 4 . 3!}{(3!)2!}\) = \(\frac{5. 4}{2. 1}\) = 10ways
(3!s cancels ou)