This is a question of 'how many combinations of nine accounts we can make from 70 accounts'
The formula for combination is given as [tex] \frac{n!}{(n-r)!r!} [/tex]
Where n is the total population = 70 accounts, and 'r' is the number of trial = 9
Substituting n = 70 and r = 9into the equation, we have
[tex] \frac{70!}{(70-9)!9!} =6503352856[/tex] ways of sampling 9 accounts (when the order does not matter)
Note: You can also use the [tex]^nC_r[/tex] button on a scientific calculator. Type in the value of n = 70, then press the [tex]^nC_r[/tex] button, then type in the value of r = 9, then press 'equal'
