posted by Devin on .
Assume that the student
has a cup with 13 writing implements: 7 pencils, 4 ball
point pens, and 2 felt-tip pens.
In how many ways can the selection be made if no more than one ball
point pen is selected?
The question is not clear.
Must he choose one of each?
Could he just take 1 pencil?
I will assume anything goes, except must be 0 ballpoint or 1 ball point
two ways to pick the ball points, either pick none or one
8 ways to pick the pencil, either pick none, or pick one, or pick 2 .... or pick 7
3 ways to pick the felt-tips, either pick one, or pick one , or pick 2
number of possible selections = 2x8x5 = 80
but that would include the 1 case of picking no pencil, picking no ballpoint and picking no felt-tip
so final number of ways = 80-1 = 79