Page 29 - 'Blast_Into_Math

Blast into Math! ets of nummers: mathematical plaagrounds

A set does not have an order associated to it; the following sets are the same

{a, b, c} = {c, b, a}.

The symbol ∈ indicates an element belongs to a set, for example

a ∈{a, b, c}.

Conversely, ∉ indicates an element does not belong to a set, for example

0 /∈{1, 2, 3}.

Sets do not have any order. A set is similar to a jar of mathematical marbles. It does not matter how the
marbles are arranged, just which marbles are in there. If we write the set whose elements are 1 and 2 as

{1, 2}

it is the same as if we write the set as

{2, 1}.

It is also the same as if we write the set as

{1, 2, 2}

or

{1, 1, 2}

or

{1, 1, 1, 2, 2, 2, 2, 2}.

A set is like a hungry jar of mathematical marbles. Once the marble jar (set) has a certain type of marble
in it (like a specific element in the set), if you put in more of the same marbles (write the same element
more than once), the jar gobbles up all the duplicate marbles (repeated elements in the set) and just
keeps one of each original marble (one of each specific element). So,

{2, 1} = {1, 2} = {1, 2, 2} = {1, 1, 2} = {1, 1, 1, 2, 2, 2, 2, 2}.

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