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If A = {a, b, c} then the number of proper subsets of A are:
  • a)
    3
  • b)
    10
  • c)
    7
  • d)
    8
Correct answer is option 'C'. Can you explain this answer?

Pooja Nair answered
  • Number of proper subsets of a given set = 2m - 1, where m is the number of elements.
  • Here the number of elements is 3. So the number of proper subsets of A = 23 - 1 = 7.

 The Shaded region in the following figure illustrates
  • a)
    A ∩ ( B ∪ C)
  • b)
    A ∩ B ∩ C
  • c)
    A ∪ B ∪ C
  • d)
    (A ∩ B) ∪ (A ∩ C)
Correct answer is option 'D'. Can you explain this answer?

New Words answered
First which region is over which region Then We will see that A is on the B so A intersection B and after C is on the A so, A intersection C after that we have to take all intersection part so A intersection B is Union with A intersection C.
The shaded region represents (A ∩ B) ∪ (A ∩ C).

Can you explain the answer of this question below:

If A = {5, 10, 15}, B = ϕ, then B – A is

  • A:

    5

  • B:

    {5,10}

  • C:

    ϕ

  • D:

    {5,10, 15}

The answer is c.

Om Desai answered
If A = {5, 10, 15}, B = ϕ
B - A will have those elements which are in B but not in A.
B - A = ϕ

 Which of the following is not an empty set?
  • a)
    {x : x is a multiple of 7, x < 7, x ∈ N}
  • b)
    Set of common points of two parallel lines in a plane
  • c)
    {x : 6 + 2x > 5x + 3, x ∈ N}
  • d)
    Set of smallest whole number
Correct answer is option 'D'. Can you explain this answer?

Ayush Joshi answered
As, the set of Whole numbers is {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...};
So, according to the set of whole numbers above, the smallest whole number should be "0" and therefore the set of smallest whole number is not empty.

For the set of all natural numbers the universal set can be
  • a)
    Set of all odd numbers
  • b)
    Set of all even numbers
  • c)
    Set of all integers
  • d)
    Set of all prime numbers
Correct answer is option 'C'. Can you explain this answer?

Krishna Iyer answered
Integers contain all the natural numbers. So it can be a universal set for natural numbers. In other options, there are only some of the elements of natural numbers.

 If ordered pair (a + 2b, 9) = (7, 3a + 2b), then the values of a and b are
  • a)
    9, 7
  • b)
    1, 3
  • c)
    7, 9
  • d)
    3, 1
Correct answer is option 'B'. Can you explain this answer?

A+2B=7------(1)
3A+2B=9------(2)
Subtracting (2) from (1)
we get, 2A=2
A=1
Subsitute A=1 in (1)
1+2B=7
2B=6
B=3
therefore A = 1, B = 3
 

For real number x and y, we writeis an irrational
number. Then the relation R is:​
a)Reflexive
b)Symmetric
c)Transitive
d)Equivalence
Correct answer is option 'A'. Can you explain this answer?

xRy => x - y + √2 is an irrational number.
Let R is a binary relation on real numbers x and y.
Now, R is transitive iff for all (x, y) ∈ R and (y, z) ∈ R implies (x, z) ∈ R
Given, xRy => x - y + √2 is irrational    ............1
and yRz => y - z + √2 is irrational       ............2
Add equation 1 and 2, we get
   (x - y + √2) + (y - z + √2) is irrational
= x - z + √2 is irrational
= xRz is irrational
So, the relation R is transitive.

The set A = {1,4,9,16,25—} in set builder form is written as
  • a)
    A = {x:x is a prime number}
  • b)
    A ={x:x is the cube of a natural number}
  • c)
    A = {x:x is the square of a natural number}
  • d)
    A = {x:x is an even natural number}
Correct answer is 'C'. Can you explain this answer?

Krishna Iyer answered
  • We know that, 12 = 1, 22 = 4, 32 = 9, 42 = 16, 52 = 25
  • Therefore the set A = {1, 4, 9, 16, 25...} can be written in set builder form as: 
    A = {x: x is the square of a natural number}

If f(x) = x2 and g(x) = cosx, which of the following is true?
  • a)
    f + g is even function
  • b)
    f – g is an odd function
  • c)
    f + g is not defined
  • d)
    f + g is an odd function
Correct answer is option 'A'. Can you explain this answer?

Raghav Bansal answered
if f(x) is an odd function
So, f(−x)=−f(x)
F(−x)=cos(f(−x))
=cos(−f(x))
=cos(f(x))
=F(x)
So cos(f(x)) is an even function
So, f(x) and g(x) is an even function

From the sets given below, select equal sets :
A = { 2, 4, 8, 12}, B = { 1, 2, 3, 4},
C = { 4, 8, 12, 14}, D = { 3, 1, 4, 2}
  • a)
    A and C
  • b)
    A and B
  • c)
    B and D
  • d)
    B and C
Correct answer is option 'C'. Can you explain this answer?

Mansi Chopra answered
 The sets are equal, if they have the exact same elements in them. Since option B & D have exactly same number of elements in them So, B & D are equal sets. 

 If U= set of all whole numbers less than 12, A=set of all whole numbers less than 10, B= Set of all odd natural numbers less than 10, then what is (A∩B)’?
  • a)
    {3,5,7,9}
  • b)
    {0,1,3,5,7,9}
  • c)
    {0,2,4,6,8,10,11}
  • d)
    {1,3,5,7}
Correct answer is option 'A'. Can you explain this answer?

Hansa Sharma answered
U = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}
A = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
B = {1, 3, 5, 7, 9}
A ∩ B = {1, 3, 5, 7, 9}
(A ∩ B)’ = U - (A ∩ B)
(A ∩ B)’ = {0, 2, 4, 6, 8, 10, 11}

 Choose the incorrect statement
  • a)
    If a set has only one element, we call it a singleton set.
  • b)
    Set of all even prime numbers is a subset of set of all natural numbers.
  • c)
    Φ is not a subset of any set.
  • d)
    Every set is a subset of itself.
Correct answer is option 'C'. Can you explain this answer?

Rohit Joshi answered
set A is a proper subset of a set B if A is a subset of B and there is at least one element of B that's not an element of A. Thus, the void set is a subset of all sets, and it's a proper subset of every set except itself

If A = {1, 2, 3}, and B = {3, 6} then the number of relations from A to B is
  • a)
    32
  • b)
    23
  • c)
    23
  • d)
    26
Correct answer is option 'D'. Can you explain this answer?

Preeti Iyer answered
The number of relations between sets can be calculated using 2mn where m and n represent the number of members in each set.
So, number of relations from A to B is 26.

Number of binary sets on the set {p, q,r} is:​
  • a)
    39
  • b)
    16
  • c)
    18
  • d)
    36
Correct answer is option 'A'. Can you explain this answer?

Guru Randhawa answered
It os must to remember these basic results the answer is 1 at 8 corners 1/8 sphere is present :8*1/8=1 that means overall( effective) one atom is present in ssc

Let R be a relation on N (set of natural numbers) such that (m, n) R (p, q)mq(n + p) = np(m + q). Then, R is​
  • a)
    An Equivalence Relation
  • b)
    Only Reflexive
  • c)
    Symmetric and reflexive.
  • d)
    Only Transitive
Correct answer is option 'C'. Can you explain this answer?

Anaya Patel answered
(m, n) R (p, q) <=> mq(n + p) = np(m + q)
For all m,n,p,q € N
Reflexive:
(m, n) R (m, n) <=> mn(n + m) = nm(m + n)
⇒ mn2 + m2n = nm2 + n2m
⇒ mn2 + m2n = mn2 + m2n
⇒ LHS = RHS
So, (m, n) R (m, n) exists.
Hence, it is Reflexive
Symmetric:
Let (m, n) R (p, q) exists
mq(n + p) = np(m + q) --- (eqn1)
(p, q) R (m, n) <=> pn(q + m) = qm (p + n)
⇒ np(m + q) = mq(n + p)
⇒ mq(n + p) = np(m + q)
This equation is true by (eqn1).
So, (p, q) R (m, n) exists
Hence, it is  not symmetric.
Transitive:
Let (m, n) R (p, q) and (p, q) R (r, s) exists.
Therefore,
mq(n + p) = np(m + q) --- (eqn1)
ps(q + r) = qr (p + s) --- (eqn2)
We cannot obtain ms(n+r) = nr(m+s) using eqn1 and eqn2.
So, ms(n + r) ≠ nr(m + s)
Therefore, (m, n) R (r, s) doesn’t exist.
Hence, it is transitive.

If n (P) = 5, n(Q) = 12 and n(P U Q) = 14 then n(P ∩ Q) =
  • a)
    3
  • b)
    4
  • c)
    5
  • d)
    7
Correct answer is option 'A'. Can you explain this answer?

Hansa Sharma answered
n (P) = 5, n(Q) = 12 and n(PUQ) = 14
n(PUQ) = n(P) + n(Q) - n(P∩Q) 
14 = 5 + 12 - n(P∩Q)
n(P∩Q) = 3

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