IGDTUW 2025 — Mathematics PYQ
IGDTUW | Mathematics | 2025If the universal set:
S={x∣−1≤x≤150}
A={multiples of 6}
B={multiples of 10}
Then how many elements are there in (A∪B)−(A∩B)?
Choose the correct answer:
- A.
30
(Correct Answer) - B.
35
- C.
40
- D.
45
30
Explanation
Solution
To solve this, we find the number of elements (n) for each set within the range 1 to 150 (since multiples are positive integers):
-
Set A (Multiples of 6): n(A)=⌊150/6⌋=25
-
Set B (Multiples of 10): n(B)=⌊150/10⌋=15
-
Set A∩B (Multiples of both 6 and 10, i.e., LCM = 30): n(A∩B)=⌊150/30⌋=5
-
Symmetric Difference (A∪B)−(A∩B):
The formula is n(A)+n(B)−2×n(A∩B).
Calculation: 25+15−2(5)=40−10=30.
The correct answer is (a) 30.
Explanation
Solution
To solve this, we find the number of elements (n) for each set within the range 1 to 150 (since multiples are positive integers):
-
Set A (Multiples of 6): n(A)=⌊150/6⌋=25
-
Set B (Multiples of 10): n(B)=⌊150/10⌋=15
-
Set A∩B (Multiples of both 6 and 10, i.e., LCM = 30): n(A∩B)=⌊150/30⌋=5
-
Symmetric Difference (A∪B)−(A∩B):
The formula is n(A)+n(B)−2×n(A∩B).
Calculation: 25+15−2(5)=40−10=30.
The correct answer is (a) 30.

