Question 1163987: U=1,2,3,4,5,6,7
A=1,2,4,5
B=1,3,5,7
How Many Elements Are In A U B'
Found 3 solutions by Edwin McCravy, solver91311, ikleyn:
Answer by Edwin McCravy(20055)   (Show Source):
You can put this solution on YOUR website!
When you list the elements in a set always put braces { }
around them. I noticed you did not do that and I put them
for you, but you should always put braces around a list of
elements.
A U B'
Substitute {1,2,4,5} for A
{1,2,4,5} U B'
Substitute {1,3,5,7} for B
{1,2,4,5} U {1,3,5,7}'
The prime ' means the complement set which is all the elements
in the universal set besides those which are in B, which are
So we replace {1,3,5,7}' by {2,4,6}
{1,2,4,5} U {2,4,6}
Union means we combine those two sets into one:
{1,2,4,5,6} <--Answer (We do not list 2 and 4 but once)
Edwin
Answer by solver91311(24713)  (Show Source):
Answer by ikleyn(52781)  (Show Source):
You can put this solution on YOUR website! .
Use the formula
n(A U B') = n(A) + n(B') - n(A ∩ B').
In the formula
n(A) = 4; n(B') = 3; n(A ∩ B') = 2.
Hence, n(A U B') = 4 + 3 - 2 = 5. ANSWER
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Be aware : in the post by John, there is a small deficiency, which makes his formula incorrect.
It is why I wrote my post.
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