If \(A=\{x\in\mathbb{N}:x\le 20,\ x\text{ is prime}\}\) and \(B=\{x\in\mathbb{N}:x<20,\ x\text{ is odd}\}\), what is \(A-B\)?
Advertisement
Answer and explanation
Correct answer: \(\{2\}\)
The primes not exceeding 20 are \(\{2,3,5,7,11,13,17,19\}\). Set \(B\) contains all odd natural numbers below 20, so it contains every odd prime in \(A\), including 19. The only element of \(A\) that is not in \(B\) is the even prime 2. Thus \(A-B=\{2\}\).
Frequently asked questions
What is the correct answer to this question?
\(\{2\}\)
Why is this the correct answer?
The primes not exceeding 20 are \(\{2,3,5,7,11,13,17,19\}\). Set \(B\) contains all odd natural numbers below 20, so it contains every odd prime in \(A\), including 19. The only element of \(A\) that is not in \(B\) is the even prime 2. Thus \(A-B=\{2\}\).
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Operations on Sets (Union, Intersection, Difference).
Advertisement