## 1. Which of the following is not a set?

### Answer:

### Explanation:

"Interesting numbers" is a subjective term and not well-defined, so it's not a set.

## 2. A set with no elements is called:

### Answer:

### Explanation:

A set with no elements is called a null set or empty set.

## 3. If A = {x: x is an even number less than 10}, then A is:

### Answer:

### Explanation:

The set A contains even numbers less than 10.

## 4. The set of all letters in the word "LETTER" is:

### Answer:

### Explanation:

In set theory, repetitive elements are counted once.

## 5. The number of subsets of the set {1, 2, 3} is:

### Answer:

### Explanation:

The subsets are {}, {1}, {2}, {3}, {1,2}, {1,3}, {2,3}, {1,2,3}.

## 6. The universal set is denoted by:

### Answer:

### Explanation:

The universal set, which often contains all the elements under consideration, is denoted by U.

## 7. If A = {1, 2, 3} and B = {3, 4, 5}, A ∩ B is:

### Answer:

### Explanation:

A ∩ B represents the intersection of sets A and B, which is the set of common elements.

## 8. The set {x: x is a prime number less than 10} is:

### Answer:

### Explanation:

Prime numbers less than 10 are 2, 3, 5, and 7.

## 9. Two sets with no common elements are called:

### Answer:

### Explanation:

Sets with no common elements are termed as disjoint sets.

## 10. If A = {1, 2} and B = {3, 4}, the Cartesian product A x B is:

### Answer:

### Explanation:

The Cartesian product A x B is the set of all ordered pairs (a,b) where a is in A and b is in B.

## 11. A set that contains an infinite number of elements is called:

### Answer:

### Explanation:

An infinite set has an endless number of elements.

## 12. If A = {x: x is a natural number less than 5}, then A is:

### Answer:

### Explanation:

The set A contains natural numbers less than 5.

## 13. The complement of set A with respect to the universal set U is denoted by:

### Answer:

### Explanation:

The complement of set A with respect to U is the set of all elements in U that are not in A.

## 14. The set of all real numbers between 1 and 10 is represented by:

### Answer:

### Explanation:

This represents all real numbers greater than 1 and less than 10.

## 15. If A = {a, b, c} and B = {b, c, d}, A ∪ B is:

### Answer:

### Explanation:

A ∪ B represents the union of sets A and B, which includes all unique elements from both sets.

## 16. If N is the set of natural numbers, then the set {x: x ∈ N, x^2 < 30} is:

### Answer:

### Explanation:

The numbers 1^2, 2^2, 3^2, and 4^2 are all less than 30, but 5^2 is 25 which is less than 30, however, 6^2 is 36 which is greater than 30.

## 17. Two sets that contain exactly the same elements are called:

### Answer:

### Explanation:

Sets that have the same elements are termed as equal sets.

## 18. The set {x: x is a vowel in the word "APPLICATION"} is:

### Answer:

### Explanation:

The vowels in the word "APPLICATION" are A and I.

## 19. If A ⊆ B, it implies:

### Answer:

### Explanation:

A ⊆ B denotes that every element of set A is also an element of set B.

## 20. If A = {1, 2, 3} and B = {4, 5}, the number of elements in the Cartesian product A x B is:

### Answer:

### Explanation:

The Cartesian product A x B will have 3×2 = 6 ordered pairs.