Which number is a prime factor of 168?

A prime factor is a factor of a number that is a prime number, meaning it has no divisors other than 1 and itself. To determine if 3 is a prime factor of 168, we need to check if 168 can be evenly divided by 3.

When we divide 168 by 3, we get:

168 ÷ 3 = 56

Since 56 is a whole number, this means that 3 is indeed a factor of 168. Additionally, because 3 is a prime number, it qualifies as a prime factor.

While 4, 6, and 10 may also be factors of 168, they are not prime numbers. The number 4 can be divided by 2, 6 can be divided by 2 and 3, and 10 can be divided by both 2 and 5, which means they all have divisors other than 1 and themselves. Thus, they do not meet the criteria for being prime factors.

Therefore, the correct choice identifies 3 as a prime factor of 168.