Coach Martin needs to pick a team for the annual Mathletes competition for this year. There are 36 tryouts for the team, 22 boys and 14 girls. Coach says that he needs a team of 4, consisting of 2 boys and 2 girls.
How many different teams can be formed?
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This problem can be split into 2 parts, the boys and the girls.
Boys
There are 22 boys and only 2 spots for them. For this we can utilise n C r where we are picking a subset of 2 (r) from a set of 22 (n) objects and, as we're picking a team, we do not care about the order. ( 2 2 2 ) = ( 2 2 − 2 ) ! ⋅ 2 ! 2 2 ! = 2 0 × 1 9 × . . . × 2 × 1 ⋅ 2 × 1 2 2 × 2 1 × . . . × 2 × 1 = 2 2 2 × 2 1 = 2 3 1
Girls
Now, we can do a similar strategy for the girls, using 14 and 2 as our value of n and r: ( 1 4 2 ) = ( 1 4 − 2 ) ! ⋅ 2 ! 1 4 ! = 1 2 × 1 1 × . . . × 2 × 1 ⋅ 2 × 1 1 4 × 1 3 × . . . × 2 × 1 = 2 1 4 × 1 3 = 9 1
Finally we need to multiply them together: ( 2 2 2 ) ( 1 4 2 ) = 2 3 1 × 9 1 = 2 1 0 2 1