How many elements are there in M = {x ∈ N : x < 40 and x is divisible by 6 or 9}?
Advertisement
Answer and explanation
Correct answer: 8
The positive multiples of 6 below 40 are 6, 12, 18, 24, 30, and 36. The positive multiples of 9 below 40 are 9, 18, 27, and 36. Taking the union gives {6, 9, 12, 18, 24, 27, 30, 36}, which has 8 elements. The common multiples 18 and 36 are counted only once because a set has no repeated elements.
Frequently asked questions
What is the correct answer to this question?
8
Why is this the correct answer?
The positive multiples of 6 below 40 are 6, 12, 18, 24, 30, and 36. The positive multiples of 9 below 40 are 9, 18, 27, and 36. Taking the union gives {6, 9, 12, 18, 24, 27, 30, 36}, which has 8 elements. The common multiples 18 and 36 are counted only once because a set has no repeated elements.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Sets and their representations.
Advertisement