Universal set $\sigma$ = {7, 8, 9, 10, 11, 12, 13, 14, 15}
A = {numbers that are multiples of 3}
B = {odd numbers}
C = {10 $\le$ number $\le$ 13}

how do I know how many numbers there are in set $A \cup B$

Question

Universal set $\sigma$ = {7, 8, 9, 10, 11, 12, 13, 14, 15}
A = {numbers that are multiples of 3}
B = {odd numbers}
C = {10 $\le$ number $\le$ 13}

how do I know how many numbers there are in set $A \cup B$

anonymous · Answer

AUB = { 7,9,11,12,13,15}

lgbasallote · Answer

???

anonymous · Answer

A={9,12,15}

B = {7,9,11,13,15}

hartnn · Answer

n(A)= 3
n(B)= 5
n(A intersection B) = 2 (9 and 15)
so n(A union B) = n(A)+n(B)- n(A intersection B) = 3+5-2 = 6

hartnn · Answer

u got that lg ?

lgbasallote · Answer

less math more words?

anonymous · Answer

hartnn's way is a analatical thing.

anonymous · Answer

it is more easy to draw a diagram..

lgbasallote · Answer

aren't there infinite numbers in set A U B?

anonymous · Answer

i think this can be more difficult for you to solve as a way of hartuun

lgbasallote · Answer

like i said before...less math more words....i really am not a ver good math learner

lgbasallote · Answer

in case you haven't noticed my "i hate math" [picture

hartnn · Answer

the universal set here is finite so how come union ever become infinite ?

lgbasallote · Answer

oh

lgbasallote · Answer

the universal set limits the elements

lgbasallote · Answer

you could have said that earlier...

anonymous · Answer

you said.. universal set is cofined in several number//

anonymous · Answer

i thought you noticed..

hartnn · Answer

yup, we see w.r.t universal set mentioned/given.

lgbasallote · Answer

i also said i didn't know what those meant

lgbasallote · Answer

so "numbers multiple of three" are the ones in the universal set?

anonymous · Answer

universal set means that total group is that number.

anonymous · Answer

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