Question

A university professor asked his class of 42 students when they had studied for his class the previous weekend. There responses were. please answer part a, b and c

Answer 1

ANSWERS:

a) 16 students

b) 25 students

c) 2 students

STEP BY STEP:

There are 42 students in total. This question can be solved by "Principal of Inclusion and Exclusion"

Question a)

The students that studied on Sunday in total with overlaps is 30. To figure out the students that ONLY studied on Sunday you need to first minus the overlaps in the combos:

the combos:

3, 10, 6, 2

Since the last combo included all of the other dates, we need to minus it:

1, 8, 4, 2

Now we can use the total of Sunday and minus the combos that includes Sunday:

30 - (4 + 2 + 8)  = 16 students

Question b)

To figure out all the students that only studied on ONE day, not 2 not 3, just one day. We need to figure out the students that studied for Saturday and Friday using the same method before for figuring out Sunday:

Friday: 9 - 4 - 1 -2 = 2 students

Saturday: 18 - 1 - 2- 8 = 7 students

and now add them all together: 2 + 7 + 16 = 25 students

That is the total number of students that studied on one day.

Question c)

Now for the numbers of students that didn't study... We can just use the total to minus everything else!

42 - (25 + 1 + 4 + 8 + 2) = 2 students!!!

And thats all done!  If you still don't get it, please ask!