Sets

We looked at Set notation, basics of Venn diagrams etc in class. If you are unsure of any of this, go back over the Sets chapter in book 1, as book 2 really just glosses over the foundations.

The big difference with Higher Level Sets is that you have to handle unknowns.
Take a class where 8 study Latin and 10 study Business. If you don't know how many study both, you put :
x in the L intersection B region of the diagram
(8 - x) in the L\B region
(10 - x) in the B\L region.
Then if you are told there are 14 students altogether you can create the equation:
(8 - x ) + x + (10 - x) = 14
and solve for x
18 - x = 14
x = 4 .... so 4 students study both Latin and Business.
You don't need the brackets in the above example, but it is a good idea to always use them as there are times you need to work out expressions like in q 13 on page 195
For the region of the Venn diagram representing W only the x - 2 is worked out from:
16 - (10 - x) - x - (8 - x)
= 16 - 10 + x - x - 8 + x
= -2 + x or x -2

Homework was p189: q11, q13