In how many ways can a team of 3 boys and 3 girls be selected from 5 boys and 4 girls?

24

Determine n if   (i) ²ⁿC₃: nC₂ = 12:1   (ii) 2nC₃ : nC₃ = 11:1.

25

How many chords can be drawn through 21 points on a circle?

27

Find the number of ways of selecting 9 balls from 6 red balls, 5 white balls and 5 blue balls if each selection consists of 3 balls of each colour.

28

Determine the number of 5 cards combinations out of a deck of 52 cards if there is exactly one ace in each combination.