How many elements are in A = {x : x ∈ ℕ, x is a multiple of both 12 and 18 and x < 100}?
Answer and explanation
Correct answer: 2
A number that is a multiple of both 12 and 18 must be a multiple of their least common multiple. Since lcm(12, 18) = 36, the positive multiples below 100 are 36 and 72. The next multiple, 108, is not less than 100. Therefore, A = {36, 72} and has 2 elements, so option B is correct.
Frequently asked questions
What is the correct answer to this question?
2
Why is this the correct answer?
A number that is a multiple of both 12 and 18 must be a multiple of their least common multiple. Since lcm(12, 18) = 36, the positive multiples below 100 are 36 and 72. The next multiple, 108, is not less than 100. Therefore, A = {36, 72} and has 2 elements, so option B is correct.
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.