Sets and their operations
Answers are for parents and teachers.
1
Write B = {x : x ∈ N, 2 < x < 8} by listing.
B = {3, 4, 5, 6, 7}.
2
List all the subsets of {7, 8, 9}. How many are there?
∅, {7}, {8}, {9}, {7, 8}, {7, 9}, {8, 9}, {7, 8, 9}: 8 subsets (2³).
3
A = {1, 2, 3, 4, 6, 12} and B = {1, 2, 4, 8}. Find A ∩ B and A ∪ B.
A ∩ B = {1, 2, 4}. A ∪ B = {1, 2, 3, 4, 6, 8, 12}.
4
How many subsets does a set with 6 elements have?
2⁶ = 64.
5
True or false: ∅ ⊂ {1, 2}. Explain.
True. The empty set has no element outside {1, 2}, so it is a subset of every set.