Highest voted questions in Discrete Mathematics

27 votes
5 answers
262
Let $G_1$ and $G_2$ be subgroups of a group $G$.Show that $G_1 \cap G_2$ is also a subgroup of $G$.Is $G_1 \cup G_2$ always a subgroup of $G$?.
27 votes
3 answers
264
Let A be a finite set of size n. The number of elements in the power set of $A\times A$ is:$2^{2^n}$$2^{n^2}$$\left(2^n\right)^2$$\left(2^2\right)^n$None of the above
27 votes
3 answers
266
Let $S$ be a set of $n$ elements. The number of ordered pairs in the largest and the smallest equivalence relations on $S$ are:$n$ and $n$$n^2$ and $n$$n^2$ and $0$$n$ an...
27 votes
4 answers
267
Consider the set $S = \{1, ω, ω^2\}$, where $ω$ and $ω^2$ are cube roots of unity. If $*$ denotes the multiplication operation, the structure $(S, *)$ formsA GroupA R...
27 votes
4 answers
268
Which one of the following is NOT necessarily a property of a Group?CommutativityAssociativity Existence of inverse for every element Existence of identity
26 votes
2 answers
274
How many true inclusion relations are there of the form $A \subseteq B$, where $A$ and $B$ are subsets of a set $S$ with $n$ elements?
26 votes
5 answers
276
26 votes
3 answers
279
What is the cardinality of the set of integers $X$ defined below?$X=\{n \mid 1 \leq n ≤ 123, n$ is not divisible by either $2$, $3$ or $5\}$$28$$33$$37$$44$
26 votes
8 answers
280
Let $A$ and $B$ be sets and let $A^c$ and $B^c$ denote the complements of the sets $A$ and $B$. The set $(A-B) \cup (B-A) \cup (A \cap B)$ is equal to$A \cup B$$A^c \cup ...