Relations and Functions Ex 1.2-10th Std Maths-Book Back Question And Answer
Question 1.
Let A = {1, 2, 3, 7} and B = {3, 0, -1, 7}, which of the following are relation from A to B?
(i) R1 = {(2,1), (7,1)}
(ii) R2 = {(-1,1)}
(iii) R3 = {(2,-1), (7, 7), (1,3)}
(iv) R4 = {(7, -1), (0, 3), (3, 3), (0, 7)}
Answer:
A = {1,2,3,7} B = {3,0,-1, 7}
A × B = {1,2,3} × {3, 0,-1, 7}
A × B = {(1,3) (1,0) (1,-1) (1,7) (2,3) (2, 0)
(2, -1) (2, 7) (3, 3) (3,0) (3,-1)
(3, 7) (7, 3) (7, 0) (7,-1) (7, 7)}
(i) R1 = {(2, 1)} (7, 1)
It is not a relation, there is no element of (2, 1) and (7, 1) in A × B
(ii) R2 = {(-1),1)}
It is not a relation, there is no element of
(-1, 1) in A × B
(iii) R3 = {(2,-1) (7, 7) (1,3)}
Yes, It is a relation
(iv) R4 = {(7,-1) (0,3) (3, 3) (0,7)}
It is not a relation, there is no element of (0, 3) and (0, 7) in A × B
Question 2.
Let A = {1, 2, 3, 4,…,45} and R be the relation defined as “is square of ” on A. Write R as a subset of A × A. Also, find the domain and range of R.
Solution:
A = {1, 2, 3, 4, . . . 45}, A × A = {(1, 1), (2, 2) ….. (45, 45)}
R – is square of’
R = {(1, 1), (2, 4), (3, 9), (4, 16), (5, 25), (6, 36)}
R ⊂ (A × A)
Domain of R = {1, 2, 3, 4, 5, 6}
Range of R = {1, 4, 9, 16, 25, 36}
Question 3.
A Relation R is given by the set {(x, y)/y = x + 3, x ∈ {0, 1, 2, 3, 4, 5}}. Determine its domain and range.
Answer:
x = {0, 1, 2, 3, 4, 5}
y = x + 3
when x = 0 ⇒ y = 0 + 3 = 3
when x = 1 ⇒ y = 1 + 3 = 4
when x = 2 ⇒ y = 2 + 3 = 5
when x = 3 ⇒ y = 3 + 3 = 6
when x = 4 ⇒ y = 4 + 3 = 7
when x = 5 y = 5 + 3 = 8
R = {(0, 3) (1,4) (2, 5) (3, 6) (4, 7) (5, 8)}
Domain = {0, 1, 2, 3, 4, 5}
Range = {3, 4, 5, 6, 7, 8}
Question 4.
Represent each of the given relations by
(a) an arrow diagram
(b) a graph and
(c) a set in roster form, wherever possible.
(i) {(x,y) | x = 2y,x ∈ {2, 3, 4, 5}, y ∈ {1, 2, 3, 4}
(ii) {(x, y) | y = x + 3, x, y are natural numbers < 10}
Answer:
(i) x = {2, 3, 4, 5} y = {1, 2, 3, 4}
x = 2y
wheny y = 1 ⇒ x = 2 × 1 = 2
when y = 2 ⇒ x = 2 × 2 = 4
when y = 3 ⇒ r = 2 × 3 = 6
when y = 4 ⇒ x = 2 × 4 = 8
(a) Arrow diagram
(b) Graph
(c) Roster form R = {(2, 1) (4, 3)}
(ii) x = {1, 2, 3, 4, 5, 6, 7, 8, 9}
y = {1,2, 3, 4, 5, 6, 7, 8,9}
y = x + 3
when x = 1 ⇒ y = 1 + 3 = 4
when x = 2 ⇒ y = 2 + 3 = 5
when x = 3 ⇒ y = 3 + 3 = 6
when x = 4 ⇒ y = 4 + 3 = 7
when x = 5 ⇒ y = 5 + 3 = 8
when x = 6 ⇒ y = 6 + 3 = 9
when x = 7 ⇒ y = 7 + 3 = 10
when x = 8 ⇒ y = 8 + 3 = 11
when x = 9 ⇒ y = 9 + 3 = 12
R = {(1,4) (2, 5) (3,6) (4, 7) (5, 8) (6, 9)}
(a) Arrow diagram
(b) Graph
(c) Roster form: R = {(1, 4) (2, 5) (3, 6) (4, 7) (5, 8) (6, 9)}
Question 5.
A company has four categories of employees given by Assistants (A), Clerks (C), Managers (M) and an Executive Officer (E). The company provide ₹10,000, ₹25,000, ₹50,000 and ₹1,00,000 as salaries to the people who work in the categories A, C, M and E respectively. If A1, A2, A3, A4 and A5 were Assistants; C1, C2, C3, C4 were Clerks; M1, M2, M3 were managers and E1, E2 were Executive officers and if the relation R is defined by xRy, where x is the salary given to person y, express the relation R through an ordered pair and an arrow diagram.
Answer:
Assistants → A1, A2, A3, A4, A5
Clerks → C1, C2, C3, C4
Managers → M1, M2, M3
Executive officers → E1, E2
R = {00000, A1) (10000, A2) (10000, A3) (10000, A4) (10000, A5)
(25000, C1) (25000, C2) (25000, C3) (25000, C4)
(50000, M1) (50000, M2) (50000, M3) (100000, E1) (100000, E2)}
(a) Arrow diagram
Functions Definition
A relation f between two non – empty sets X and Y is called a function from X to Y if for each x ∈ X there exists only one Y ∈ Y such that (x, y) ∈ f
f = {(x, y) / for all x ∈ X, y ∈ f}
Note: The range of a function is a subset of its co-domain
