Question

which is the set of natural numbers that are factors of 20?
{1, 2, 4, 5, 10, 20}
{20, 40, 60, 80, ...}
{2, 4, 5, 10}
{5, 10, 20}

Explanation:

Step1: Define factors of 20

Factors are natural numbers that divide 20 without remainder.

Step2: List all divisors of 20

Test natural numbers: $1$ divides $20$ ($20\div1=20$), $2$ divides $20$ ($20\div2=10$), $4$ divides $20$ ($20\div4=5$), $5$ divides $20$ ($20\div5=4$), $10$ divides $20$ ($20\div10=2$), $20$ divides $20$ ($20\div20=1$).

Step3: Match to options

The full set is $\{1, 2, 4, 5, 10, 20\}$.

Answer:

$\{1, 2, 4, 5, 10, 20\}$