Answer: 3 x 5
Step-by-step explanation: To find the prime factorization of 15, first create a factor tree with two branches. Since 15 ÷ 3 = 5, we know that 3 and 5 are factors of 15. So we write 3 and 5 at the bottom of the branches.
While 1 and 15 are also factors, we don't use them in out factor tree. That's because when finding the prime factorization, we always use numbers other than 1 and the number itself.
Next, we circle any prime factors in the factor tree. Since both 3 and 5 are prime, we circle both 3 and 5. Since we have circles at the bottom of all of our branches, we are finished.
So the prime factorization of 15 is 3 x 5.
Notice that we write our prime factorization as a multiplication problem. Think of the prime factorization of a number as the prime factors of the number that you multiply together to get the original number.
