Union

Q.

The operation in which the elements that are either in set A or in set B or in both set A and set B is called ____.

1. Union of two sets

2. Intersection of two sets

3. Difference between two sets

4. None

Q.

Let A = {1, 2, 3, 4, 5, 6} and B = {2, 4, 6, 8}. Then the sets $A\cup B$ and $A\cap B$ are

1. {2, 4, 6}; {2, 4, 6}

2. {1, 5}; {8}

3. {1, 3, 5}; {8}

4. {1, 3, 5}; {2, 4, 6}

Q. Three numbers which are co-prime to each other are such that the product of the first two is 551 and that of the last two is 1073. The sum of the three numbers is:

1. $65$
2. $55$
3. $85$
4. $75$

Q. How many prime numbers less than $100$ leave an odd remainder when divided by $5$?

1. $11$
2. $12$
3. $13$
4. $14$

Q. The only prime number which is even is

1. $2$
2. $4$
3. $6$
4. none of these

Q. Express 216 as a product of power of prime factors .

Q. Find the prime factorization of $120$.

Q. The number of divisors of $2156$ which are even but not divisible by $11$ is

1. $9$
2. $6$
3. None of the above
4. $18$

Q. I am a prime number.I am a factor of $56$.I am not a multiple of $7$.What number am I?

Q. $18$ is divisible by both $2$ and $3$.It is also divisible by $2\times 3=6.$ Similarly, a number is divisible by both $4$ and $6.$ Can we say that the number must also be divisible by $4\times 6=24$?If not, give an example to justify your answer.

Q. Which pairs are not co-prime number?

1. $22,44$
2. $13,97$
3. $175,221$
4. $73,37$.

Q. If $x$ and $y$ are positive integers such that $x$ is an odd prime and $y$ is composite, then which of the following is true?

1. $y-x$ cannot be an even integer
2. $xy$ cannot be an even integer
3. $x+y$ is an integer
4. $\frac{(x+y)}{x}$ cannot be an even integer

Q. How do you find the GCF of $20$ and $30$?

Q. Scientists can break atoms to get still smaller particles. In the light of what you have read in this chapter, do you think that a broken atom of say gold, will have the same properties as an atom of gold?

Q. If $y=30p$, and $p$ is prime, what is the greatest common factor of $y$ and $14p$, in terms of $p$?

Q. The product of two whole numbers is $13$. What is the sum of the squares of their reciprocals?

1. $\frac{170}{169}$
2. $\frac{173}{169}$
3. $\frac{171}{169}$
4. $\frac{172}{169}$

Q. Relatively prime integers is -

1. $6,9$
2. $4,9$
3. $7,28$
4. $8,12$