Question

Assume that n(U) = 90, n(A) = 40, and n(B) = 45.
Then n( A′∪B) = ??

Answer 1

I thought A' would be 50 because 90-40=50 and B is 45, so 45+50=95, but apparently that isn't correct!

Answer 2

U is the universal set. It is everything. So you can't get more than 90

if you get 95, it must mean that some of B are also in A.

Answer 3

A^c = (U-A)

Answer 4

Clearly I wasn't thinking! Alright, so how would I find the answer for this?

Answer 5

90-(40+45)=90-85=5

Answer 6

5 would be what in this?

Answer 7

answer of n(a' union b)

Answer 8

I think I get it. Thanks!

Answer 9

@Wislar did u got it

Answer 10

This doesn't seem to be working out. Wouldn't 5 actually be (A U B)'?

Answer 11

Would it be 50?

Answer 12

Is there any more info? Because this picture (for example) seems to fit:

which gives 80 as the answer