Question

A number is between 17 and 22. It has prime factors of 2, and 5. What is the number? (Type a whole number.)

Answer 1

$\begin{gathered} Between\text{ 17 and 22, there are four numbers:} \\ 18,19,20,21 \\ the\text{ number 19 is prime, so the possibilities are} \\ 18,20,21 \\ \text{However, 5 is not factor of 18 nor 21. Hence, the only CHOICE is 20} \end{gathered}$