Let R={3,4,5,6,7,8,9} ,S={1,3,5} and T={ 2,4,6,8}

Question

Let R={3,4,5,6,7,8,9} ,S={1,3,5} and T={ 2,4,6,8}
a)R ∩ S
b)R – T
c)S ∪ T

Answer 1

Hi Daniel!  It looks like you're studying sets and set notation.

 

a.  ∩ means the "intersection of the sets" and refers to the values that are in both sets.  {16,17,18,19} ∩ {14,16,18,20} would be {16,18}, because 16 and 18 are found in both {16,17,18,19} and {14,16,18,20}.  Your question asks for the intersection of {3,4,5,6,7,8,9} and {1,3,5}.  Which digit(s) are in both lists (or sets) of numbers?

 

b.  - means the "difference between sets" and refers to all of the values that are in the first set but not the second set.  {16,17,18,19} - {14,16,18,20} would be {17,19} because the 17 and 19 from {16,17,18,19} aren't found in {14,16,18,20}.  Your question asks for the difference between {3,4,5,6,7,8,9} and {2,4,6,8}.  What digit(s) in the first set aren't included in the second set?

 

c.  ∪ means the "union of the sets" and refers to the list of all unique values from both sets.  {16,17,18,19} ∪ {14,16,18,20} would be {14,16,17,18,19,20} because these are the six numbers that are found somewhere within the two sets.  Notice that 16 and 18 aren't repeated in the solution, even though they both show up twice (in the original sets).  Your question asks for the union of {1,3,5} and {2,4,6,8}.  What set of numbers includes all of the unique digits from these two sets?

 

Hope this helps!

 

Bill