Question 1088890
There are {{{15*14*13*12/(4*3*2)=15*13*7}}} possible sets of 4 basketball team members.
How many possible sets of 4 basketball team members can be made consisting of one member of each class?
There are 7 possible choices for the senior, 
3 possible choices for the junior,
3 possible choices for the sophomore,
and 2 for the freshman,
meaning {{{7*3*3*2}}} possible sets of 4 basketball team members with one person from each class.
The probability of randomly selecting such a set of 4 team members is
{{{7*3*3*2/(15*13*7)=3*3*2/(15*13)=3*2/(5*13)=6/65="0.0923076923076923076...."}}} .
Rounding to 2 decimal places, it is {{{highlight(0.09)}}} or 9% .