Think And Discuss
An empty set is a finite set. Is this statement true or false? Why?
EXERCISE - 2.4
1. State which of the following sets are empty and which are not?
(i) The set of lines passing through a given point.
(ii) Set of odd natural numbers divisible by 2.
(iii) {x : x is a natural number, x < 5 and x > 7}
(iv) {x : x is a common point to any two parallel lines}
(v) Set of even prime numbers.
2. State whether the following sets are finite or infinite.
(i) The set of months in a year.
(ii) {1, 2, 3, …, 99, 100}
(iii) The set of prime numbers smaller than 99.
(iv) The set of letters in the English alphabet.
(v) The set of lines that can be drawn are parallel to the X-Axis.
(vi) The set of numbers which are multiplies of 5.
(vii) The set of circles passing through the origin (0, 0).
Example-14.
If A = {1, 2, 3,4,5}; B = {2,4,6,8} then find n(A ∪ B).
Solution
: The set A contains five elements therefore, n(A) = 5
and the set B contains four elements therefore, n(B) = 4
But A ∪ B={1,2,3,4,5,6,8} does not contain 9 elements and it contains 7 elements only. Why?
page no:48
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