Question

Find the number of ways of selecting 3 pairs from 8 distinct objects.

Answer 1

Number of ways of selecting first pair of objects `= .^(8)C_(2)`
Number of ways of selecting second pair of objects `= .^(6)C_(2)`
Number of ways of selecting third pair of objects `= .^(4)C_(2)`
`therefore` Number of ways `=(.^(8)C_(2)xx .^(6)C_(2) xx .^(4)C_(2))//3!`, since the order in which pairs are selected is immaterial.