Algebra with applications
posted by lyn .
A poll was taken of 100 students at a commuter campus to find out how they got to campus. The results were as follows:
23 said they drove alone.
30 rode in a carpool.
31 rode public transportation.
4 used both carpools and public transportation.
3 used both a carpool and sometimes their own cars.
3 used buses as well as their own cars.
1 used all three methods.
How many used none of the abovementioned means of transportation?

drove alone  A
carpool  B
public trans C
number(A or B or C) = number A + number B + number C  Number (AandB)  number (Aand C)  number (Band C) + number (AndBandC)
= 23 +30 +31  4  3  3 + 1
= 75
so 100  75 or 25 used none of the above