Question

PLEASE HELP!!!!

Given A and B, use your knowledge of sets to determine which one of the following numbers is not in
AUB.
A = {-10, 8, 12, 26, 29}
B = {-8, - 1,5, 26, 36}


A.18
B. -10
C. 26
D. 36
E. None of the above

Answer 1

Answer: A. 18

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Step-by-step explanation:

The set A U B represents the list of items that are either in set A, set B or both sets at the same time. The "U" is the union symbol.

Set A U B looks like this

A U B = {-10, 8, 12, 26, 29, -8, - 1,5, 26, 36}

I basically started with set A, then tacked on the stuff in set B shown in bold.

From here, we toss out the duplicate item 26 and we can optionally sort the set

A U B = {-10, -8, -1, 5, 8, 12, 26, 29, 36}

We see that the number 18 is not in this final set, which is why choice A is the answer.

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Put another way: the number 18 is neither in set A nor set B, so it cannot be in set A U B.

Something like -10 is in set A, so it's going to be in set A U B as well. We can rule out choice B for this reason. Choices C and D follow a similar idea as choice B.