I understand that {1, 2}={1, 2, 1}.

But do they have the same number of elements??????

Please help!!! Many thanks!!

Printable View

- Oct 20th 2006, 03:11 AMacc100jtCounting elements
I understand that {1, 2}={1, 2, 1}.

But do they have the same number of elements??????

Please help!!! Many thanks!! - Oct 20th 2006, 03:57 AMCaptainBlack
If these are sets yes they have the same elements, and so the

same number of elements. The elements of {1, 2} are 1 and 2, and

the elements of {1, 2, 1} are 1 and 2. But we would not normally

write something like {1, 2, 1} when talking about sets, so maybe

your question is really about something else?

RonL - Oct 20th 2006, 04:05 AMThePerfectHacker
Perhaps he was told to prove that,

$\displaystyle \{1,2\}=\{1,2\}$

Have the same number of elements?

------

If so then consider the map,

$\displaystyle \phi:\{1,2\}\to \{1,2\}$

defined as, $\displaystyle \phi(1)=1$ und $\displaystyle \phi(2)=2$. Then it is a bijective map. And the prove is complete. - Oct 20th 2006, 04:15 AMOReilly
They have same elements, but why do they have same number of elements?

If we are talking about different elements then they have same number of elements. Talking about quantity then we have different number of elements. First set has 2 and second set has 3 elements.