Name: Susan

Who is asking: Parent
Level: All

Question:
My child has the following problems to solve, and we are puzzled.
1. Compare the subset symbols to the inequality symbols of less than or greater than.

2. If A, B & C are sets such that A has 47 elements, B has 32 elements, and C is a proper subset of B, what can you say about the number of elements in the following sets: A U B? A intersect B? B U C? and B intersect C?

Thanks so much!

Hi Susan,

1. If A is a subset of B then the number of elements in a is less than or equal to the number of elements of B, so a better camparison might be between the subset symbol and the "less than or equal to" sumbol. One place wher there is a comparison is that if A is a subset of B and B is a subset of C then A is a subset of C. The same relationship is true with less than. If a is less than b and b is less than c then a is less than c.
   
2. I am going to use the notation |D| to mean the number of elements in the set D and <= for "less than or equal to".
   
   The best you can say is that
   47 <= |AUB| <= 79
   0 <= |A intersect B| <= 32
   BUC = C so |BUC| = 32
   B intersect C is C so |B intersect C| = |C|

Go to Math Central