Question

Which of the following is true? twenty-one is a composite number because one and twenty-one are its only factors. thirteen is a prime number because it is only divisible by one and itself. sixteen is a prime number because it is divisible by 4. twenty-eight is a composite number because eighty-two is a prime number.

Answer 1

Which of the following is true?

twenty-one is a composite number because one and twenty-one are its only factors.

thirteen is a prime number because it is only divisible by one and itself.

sixteen is a prime number because it is divisible by 4.

twenty-eight is a composite number because eighty-two is a prime number.

Answer 2

Whole numbers are either prime or composite.
A prime number is a number that has exactly two factors, 1 and itself.
A composite number has more than 2 factors.

Answer 3

Thirteen is a prime number, because it's only factors are 1 and itself

Answer 4

Look at the number 21.
Can you list all its factors?
What are all the numbers 21 is divisible by in addition to 1 and 21?

Answer 5

thank you

Answer 6

@mathstudent55 has a much better response than me, listen to him :)

Answer 7

@1lorax2 Thanks of the compliment.

Answer 8

Of course, I'm always ready to defer to somebody who's better equipped than myself to deal with a problem.

Answer 9

Factors of 21: 1, 3, 7, 21. More than 2 factors. It is a composite number.
Factors of 13: 1, 13. Exactly 2 factors. Prime number.
Factors of 16: 1, 2, 4, 8, 16. More than 2 factors. Composite number.
Factors of 28: 1, 2, 4, 7, 14, 28. More than 2 factors. Composite number.

Answer 10

I have a question. Is 1 prime or not?

Answer 11

What is the Least Common Denominator (LCD) of nine-sixteenths and nineteen twenty-fourths?

forty-eight

thirty-two

sixteen

4

Answer 12

If I remember right, I believe that 1 is a category all it's own.

Answer 13

0 is composite, 1 is special, 2 is the only even prime, and so on and so forth

Answer 14

thank you

Answer 15

Correct. 1 is not prime because it does not have exactly 2 different factors. There is only one factor of 1, and it is 1.

Answer 16

Now for the second question.
The denominators are 16 and 24.
You need to find the smallest number that is a multiple of both.

Answer 17

To find the least common denominator, you have to factor both denominators. Then you choose the smallest factor that the two number have in common

Answer 18

There are several ways of doing this.
One way is list some multiples of both numbers until you find the firtt multiple that is common to both.

Answer 19

To find multiples of a number, just multiply the number by 1, 2, 3, 4, ...

Answer 20

Oh my gosh. I was completely wrong again. I don't even know what I was thinking of there- there's no operation that is similar. I completely defer to @mathstudent55 , so listen to him @swaggy_jackson

Answer 21

Here are the first several multiples of 16 and of 24:
16, 32, 48, 64, 80, 96
24, 48, 72, 96, 120
Notice the smallest multiple they both have in common is 48.
That means 48 is the LCD.

Answer 22

This is one method.
There are other methods.

Another method of finding the LCD of two numbers is to first factor the two numbers into their prime factorizations.

Answer 23

I'll use your problem as an example.
We are looking for the LCD of 16 and 24, so we factor 16 and 24 into their prime factorizations.

Answer 24

The prime factorizations are:

\(16 = 2^4\)

\(24 = 2^3 \times 3\)

Answer 25

For the LCD, we take common factors with the highest exponent, and non-common factors.

Common factors: 2 and 2. We need the higher exponent, so we pick \(2^4\).
Non-common factors: there is only one, and it's 3, so we use it too.

LCD = \(2^4 \times 3 = 16 \times 3 = 48\)