Question

A dance instructor chose four of his 10 students to be on stage for a performance.

If order does not matter, in how many different ways can the instructor choose the four students?

10 C 4 = StartFraction 10 factorial Over (10 minus 4) factorial 4 factorial

210
1,260
6,300
25,200

Answer 1

Number of ways = C(10,4) = 10!/(6!4!) = (10·9·8·7)/(4·3·2·1) = 5040/24 = 210.