A subset of a set The requirement is that all elements in the subset are also elements of the set. We can list all the subsets starting with the ones having 0 elements, followed by 1, 2, and 3 elements.
Zero-Element Subsets
The only subset of any set with zero elements is the empty set. We write this using the empty set notation.
∅
One-Element Subsets
There are 3 elements in our original set. We can use each of these to form the single element subsets.
{red}, {blue}, {yellow}
Two-Elements Subsets
Next, we need to find all the two-elements subsets.
{red, blue}, {red, yellow}, {blue, yellow}
Three-Elements Subsets
The original set has 3 elements, so we can only form one subset having 3 elements, the original set itself.
{red, blue, yellow}
Summary
We have a total of 8 subsets.
& ∅, {red}, {blue}, {yellow},
&{red, blue}, {red, yellow}, {blue, yellow}, & {red, blue, yellow}
