# What numbers between 11 and19 are composite numbers?

Jun 5, 2017

Between $11$ and $19$ we have $12 , 14 , 15 , 16 , 18$ as composite numbers.

#### Explanation:

Compossite numbers are those numbers who have factors other than $1$ and themselves.

As even numbers are multiples of $2$, between $11$ andd $19$

we have $12 , 14 , 16 , 18$ as composite numbers

among odd numbers $13 , 15 , 17$

only $15$ has factors other than $1$ and itself.

Hence, between $11$ and $19$ we have $12 , 14 , 15 , 16 , 18$ as composite numbers.

Jun 5, 2017

$12 , 14 , 15 , 16 \mathmr{and} 18.$

#### Explanation:

Composite Numbers are those numbers which have factors other than one and itself.

Example : 4 is a composite number as it has factors 1, 2 and 4.
(In fact it is the smallest composite number.)

Between $11 \mathmr{and} 19$, there are $7$ numbers:

$12 , 13 , 14 , 15 , 16 , 17 , 18$

Here $11$ is not composite, instead it is prime (those numbers which have only $1$ and themselves as factors)
[$11$ has only two factors, $1 \mathmr{and} 11$.]

$12$ is composite; as $12$ has factors $1 , 2 , 3 , 4 , 6 \mathmr{and} 12.$

$13$ is again prime, having only $1 \mathmr{and} 13$ itself as factors.

$14 \text{ has } 1 , 2 , 7 \mathmr{and} 14$
$15 \text{ has } 1 , 3 , 5 \mathmr{and} 15$
$16 \text{ has } 1 , 2 , 4 , 8 \mathmr{and} 16$
These are all composite numbers.

$17$ is prime

$18$ is composite.

Jun 5, 2017

$12 , \text{ "14," "15," "16," "18," }$

#### Explanation:

The numbers 'between' $11 \mathmr{and} 19$ are:

$12 , \text{ "13," "14," "15," "16," "17," "18," }$

All numbers (except 1) are either prime or composite.

Prime numbers have exactly $2$ factors while
Composite numbers have more than $2$ factors.

There are more composite numbers than prime numbers, so the quickest way to find the composite numbers in a given set, is to simply exclude the primes.

The prime numbers between $11 \mathmr{and} 19$ are:

$\textcolor{b l u e}{13 \mathmr{and} 17}$, so all the rest are composite.

$12 , \text{ "cancelcolor(blue)(13)," "14," "15," "16," "cancelcolor(blue)(17)," "18," }$