Question

What number do you get when you multiply the distinct (different) prime factors of $28$?

• A. $9$
• B. $4$
• C. $7$
• D. $14$
• E. $28$

Answer 1

The correct option is D $14$

To determine the prime factors of $28$, either use a factor tree, or list all the factors of $28$ and pick out the factors that are prime.

Only $2$ and $7$ are prime, so the answer is $2\times 7=14$.

Note that if you use a factor tree, you will find that the prime factors of $28$ are $2,2$, and $7$.

However, the question wants the distinct prime factors, which are just $2$ and $7$.