Solution: Let's say A, B and C are the set of people who like product A, product B and product C respectively. So now, as per the question, n (A) = 21 be Number of students who like product A, n (B)...
In a survey of 60 people, it was found that 25 people read newspaper H, 26 read newspaper T, 26 read newspaper I, 9 read both H and I, 11 read both H and T, 8 read both T and I, 3 read all three newspapers. Find: (i) The number of people who read at least one of the newspapers. (ii) The number of people who read exactly one newspaper.
Solution: (i) Let's suppose that, The set of people who read newspaper H = A The set of people who read newspaper T = B The set of people who read newspaper I = C As per the question, $n (A) = 25$ =...
In a group of students, 100 students know Hindi, 50 know English and 25 know both. Each of the students knows either Hindi or English. How many students are there in the group?
Solution: Let's suppose that, The set of all students in the group be U The set of students who know English be E $\therefore \mathrm{H} \cup \mathrm{E}=\mathrm{U}$ Provided that, $n(H)=100$ =...
In a survey of 600 students in a school, 150 students were found to be taking tea and 225 taking coffee, 100 were taking both tea and coffee. Find how many students were taking neither tea nor coffee.
Solution: Let's suppose that, The set of all students who took part in the survey be U The set of students taking tea be T The set of the students taking coffee be C Therefore, the total number of...
Find sets A, B and C such that A ∩ B, B ∩ C and A ∩ C are non-empty sets and A ∩ B ∩ C = Φ.
Solution: Let's suppose, $A\{0,1\}$ $B=\{1,2\}$ And, $C=\{2,0\}$ As per the question, $A \cap B=\{1\}$ $B \cap C=\{2\}$ And, $A \cap C=\{0\}$ $\therefore A \cap B, B \cap C$ and $A \cap C$ are not...
Let A and B be sets. If A ∩ X = B ∩ X = ϕ and A ∪ X = B ∪ X for some set X, show that A = B. (Hints A = A ∩ (A ∪ X) , B = B ∩ (B ∪ X) and use Distributive law)
Solution: As per the question, Let's say $A$ and $B$ are two sets such that $A \cap X=B \cap X=\phi$ and $A \cup X=B \cup X$ for some set $X$ We need to show, $A=B$ Proof: $\begin{array}{l} A=A...
Show that A ∩ B = A ∩ C need not imply B = C.
Solution: Let's suppose, $\begin{array}{l} A=\{0,1\} \\ B=\{0,2,3\} \end{array}$ And, $C=\{0,4,5\}$ As per the question, $A \cap B=\{0\}$ And, $\begin{array}{l} A \cap C=\{0\} \\ \therefore A \cap...
Using properties of sets, show that: (i) A ∪ (A ∩ B) = A (ii) A ∩ (A ∪ B) = A.
Solution: (i) We need to show: $A \cup(A \cap B)=A$ As it is known that, $\begin{array}{l} A \subset A \\ A \cap B \subset A \\ \therefore A \cup(A \cap B) \subset A..........(i) \end{array}$ Also,...
Show that for any sets A and B, A = (A ∩ B) ∪ (A – B) and A ∪ (B – A) = (A ∪ B)
Solution: We need to Prove, $A=(A \cap B) \cup(A-B)$ Proof: Let $x \in A$ We need to show $X \in(A \cap B) \cup(A-B)$ In Case I, $X \in(A \cap B)$ $\Rightarrow X \in(A \cap B) \subset(A \cup B)...
Assume that P (A) = P (B). Show that A = B
Solution: We need to show, $A=B$ As per the question, $P(A)=P(B)$ Let's say $x$ is any element of set $A$, $x \in A$ As, $P(A)$ is the power set of set $A$, it has all the subsets of set $A$. $A \in...
Show that if A ⊂ B, then C – B ⊂ C – A.
Solution: We need to show, $C-B \subset C-A$ As per the question, Let's suppose that $x$ is any element such that $X \in C-B$ $\therefore x \in C$ and $x \notin B$ As, $A \subset B$, we get,...
Show that the following four conditions are equivalent: (i) A ⊂ B (ii) A – B = Φ (iii) A ∪ B = B (iv) A ∩ B = A
Solution: As per the question, We need to prove, $(i) \mapsto$ (ii) Given here, $(i)=A \subset B$ and $(i i)=A-B \neq \phi$ Let's suppose that $A \subset B$ We need to prove, $A-B \neq \phi$ Let's...
Let A, B and C be the sets such that A ∪ B = A ∪ C and A ∩ B = A ∩ C. show that B = C.
Solution: As per the question, $A \cup B=A \cup C$ And, $A \cap B=A \cap C$ We need to show that, $B=C$ Let's suppose, $x \in B$ Therefore, $\begin{array}{l} x \in A \cup B \\ x \in A \cup C...
In each of the following, determine whether the statement is true or false. If it is true, prove it. If it is false, give an example. (i) If x ∈ A and A ⊄ B, then x ∈ B (ii) If A ⊂ B and x ∉ B, then x ∉ A
Solution: (i) The statement is false As per the question, $x \in A$ And also, $A \not \subset B$ Let's suppose that, $A=\{3,5,7\}$ Also here, $B=\{3,4,6\}$ It is known that, $A \not \subset B$...
In each of the following, determine whether the statement is true or false. If it is true, prove it. If it is false, give an example. (i) If A ⊂ B and B ⊂ C, then A ⊂ C (ii) If A ⊄ B and B ⊄ C, then A ⊄ C
Solution: (i) The statement is true As per the question $A \subset B$ and $B \subset C$ Let's suppose that, $x \in A$ Therefore, we have, $x \in B$ And $x \in C$ As a result, $A \subset C$ (ii) The...
In each of the following, determine whether the statement is true or false. If it is true, prove it. If it is false, give an example. (i) If x ∈ A and A ∈ B, then x ∈ B (ii) If A ⊂ B and B ∈ C, then A ∈ C
Solution: (i) The statement is false As per the question, $A\text{ }=\text{ }\left\{ 1,\text{ }2 \right\}$ and $B\text{ }=\text{ }\left\{ 1,\text{ }\left\{ 1,\text{ }2 \right\},\text{ }\left\{ 3...
Decide, among the following sets, which sets are subsets of one and another: A = {x: x ∈ R and x satisfy }, B = {2, 4, 6}, C = {2, 4, 6, 8…}, D = {6}.
Solution: As per the question, A $=$ {x: x ∈ R and x satisfies $x2 {-} 8x + 12 =0$} The only solutions of $x2 {-} 8x + 12 = 0$ are 2 and 6. As a result, A $=$ {2, 6} B $=$ {2, 4, 6}, C $=$ {2, 4, 6,...