Answer: 3 × 5
Step-by-step explanation: To find the prime factorization of 15, first create a factor tree with two branches.
Since 15 divided by 3 gives us 5, we know that and 5 are factors of 15. This means that we can write 3 and 5 at the bottom of our branches.
While 1 and 15 are also factors of 15, we don't use them in our factor tree. This because when finding a prime factorization, we only want factors other than 1 and the number itself.
Next, we circle any prime numbers in our factor tree. Since 3 and 5 are both prime numbers, we circle both 3 and 5. Since we have circles at the bottom of our branches, we are finished.
Therefore, the prime factorization of 15 is 3 × 5.