If A₁ = {x : x ∈ ℕ, x is a multiple of both 10 and 15}, what type of set is A₁?
Answer and explanation
Correct answer: Infinite
A number that is a multiple of both 10 and 15 must be a multiple of their least common multiple. Since lcm(10, 15) = 30, the set is A₁ = {30, 60, 90, 120, ...}. There is no upper bound on x, so new common multiples can always be found by continuing the sequence. Therefore, A₁ is an infinite set.
Frequently asked questions
What is the correct answer to this question?
Infinite
Why is this the correct answer?
A number that is a multiple of both 10 and 15 must be a multiple of their least common multiple. Since lcm(10, 15) = 30, the set is A₁ = {30, 60, 90, 120, ...}. There is no upper bound on x, so new common multiples can always be found by continuing the sequence. Therefore, A₁ is an infinite set.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: The Empty Set, Finite and Infinite Sets, Equal Sets.