U = {1, 2, 3, ..., 36}, A = {x : x is divisible by 2}, and B = {x : x is divisible by 3}. What is n(A ∩ B)?
Answer and explanation
Correct answer: 6
A number in A ∩ B must be divisible by both 2 and 3. Such numbers are multiples of lcm(2, 3) = 6. Within U, the multiples are 6, 12, 18, 24, 30, and 36. There are 36 ÷ 6 = 6 such numbers, so n(A ∩ B) = 6. The other choices count a different set or do not use the common condition.
Frequently asked questions
What is the correct answer to this question?
6
Why is this the correct answer?
A number in A ∩ B must be divisible by both 2 and 3. Such numbers are multiples of lcm(2, 3) = 6. Within U, the multiples are 6, 12, 18, 24, 30, and 36. There are 36 ÷ 6 = 6 such numbers, so n(A ∩ B) = 6. The other choices count a different set or do not use the common condition.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).