# Question relating to sets

• Oct 20th 2007, 11:35 AM
Kaleem Qureshi
Question relating to sets
Given that U={x : x is an integer, 2< x < equels to 18)
A = {x : 5 < equals to x < 17}
and P = A's power c, list the elements of the following :

1) A
2) P's power c
3) {Number divisible by 4}

thanks.
• Oct 20th 2007, 12:43 PM
topsquark
Quote:

Originally Posted by Kaleem Qureshi
Given that U={x : x is an integer, 2< x < equels to 18)
A = {x : 5 < equals to x < 17}
and P = A's power c, list the elements of the following :

1) A
2) P's power c
3) {Number divisible by 4}

thanks.

1) For this one what are the possible values of x?
2) A question: what does "A's power c" mean? This is not clear.
3) Which values of x are divisible by 4?

And what does any of this have to do with the set U?

-Dan
• Oct 20th 2007, 12:46 PM
Plato
Although you post is almost unreadable does it mean;
$\displaystyle U = \left\{ {3,4,5, \cdots ,17,18} \right\},\;A = \left\{ {5,6,7, \cdots 16} \right\},\;P = A^c$?

That is, the universe is the set of integers from 3 to 18; A is the subset from 3 to 16; and P is the complement of A.
• Oct 21st 2007, 07:49 AM
Kaleem Qureshi
Hi guyes,

Yes Plato, you are right here:

Set U = {3,4,5,6,7,8,9,.....18}
Set A = {5,6,7,8,9,..........16}
Set P = P's power c

But problems now is that, what would be the elements of Set P's power c

and if i am not wrong i should take for question-3, ={Number divisible by 4}
from universal set or not ?
So, if I am right then answer to question-3 would be {4,8,12,16}

Thanks for your guidance and support.
• Oct 21st 2007, 07:57 AM
topsquark
Quote:

Originally Posted by Plato
That is, the universe is the set of integers from 3 to 18; A is the subset from 3 to 16; and P is the complement of A.

I have a question: How does one know what the "universe of discourse" is unless it is stated? For example, how do we know that the compliment of A is not R\A?

-Dan
• Oct 21st 2007, 08:05 AM
Kaleem Qureshi
hello,

yes, that is the problem i am also facing, i this question there is no value given for 'c'. What we know here, is that P= Set A, but what about the power of A means 'c', what to do about it.

This needs your consideration, I am stuck.
• Oct 21st 2007, 08:30 AM
Plato
Quote:

Originally Posted by topsquark
I have a question: How does one know what the "universe of discourse" is unless it is stated?

It is purely a matter of convention in elementary set theory texts.
The letter U is used for the universe.

Quote:

Originally Posted by Kaleem Qureshi
this question there is no value given for 'c'. What we know here, is that P= Set A, but what about the power of A means 'c', what to do about it.

$\displaystyle P = A^c = \left\{ {3,4,17,18} \right\}$
• Oct 24th 2007, 03:04 AM
cu4mail
http://www.mathhelpforum.com/math-he...e2d27053-1.gif

But we have to find the compliment of P which should be values in universal table not present in compliment of A. Am I right?

can u pleae help me how to write the math funcitons in forum?
• Oct 24th 2007, 05:22 AM
Plato
You are given that $\displaystyle P = A^c$.
So $\displaystyle P^c = \left( {A^c } \right)^c = A$