Question

a poll was taken of 100 students at a computer campus to find out how they got to campus.
31 said they drove alone
34 rode in a carpool
25 rode public transportation
5 used both carpool and public transportation
8 used both a car pool and sometimes their own cars
4 used buses as well as their own cars
3 used all methods
how many used none of the above mentioned means of transportation

Answer 1

No Emmily, how can you have -10 people ?

Make a Venn diagram, showing three overlapping circles, label them
A for driving alone
C for carpool
P for public trans

put 3 in the intersection of all 3 circles
5 used C and P, so 5 goes in that intersection, BUT 3 are already counted, so place 2 in the outer part of the intersection of C and P
in the same way, place 1 in the outer part of A and P
in the same way , place 5 in the outer part of A and C
now each circle itself
A should have a total of 31, but I already have 9 counting in the A circle, leaving 22 in the unused part of A
C should have 34, but I already have 10 filled in, leaving 24 for the rest of circle C
P should have 25, but I already have 6 filled in, leaving 19 for the rest of circle P

Adding up all the numbers I see filled in, I get 76
so from the 100 students, 24 do not use any of the 3 methods.