To reduce the ratio $17:102$ to its simplest form, we need to find the greatest common divisor (GCD) of 17 and 102 and divide both numbers by that GCD.

1. Find the GCD of 17 and 102:
   Since 17 is a prime number, the only possible divisors of 17 are 1 and 17 itself. Now, check if 17 divides 102:

   $102 \div 17 = 6$

   So, the GCD of 17 and 102 is 17.

2. Divide both terms by the GCD (17):
   $\frac{17}{17} : \frac{102}{17} = 1 : 6$

Thus, the ratio $17:102$ simplifies to $1:6$.

Would you like any further explanations or examples? Here are some follow-up questions:

1. How do you find the GCD of two numbers using prime factorization?
2. Can you simplify a ratio of mixed numbers (e.g., 5 1/2 : 3 1/4)?
3. What is the role of prime numbers in simplifying ratios?
4. How do you simplify ratios that are not whole numbers?
5. What is the relationship between fractions and ratios?

Tip: To simplify a ratio or fraction, always start by finding the GCD of the numbers involved.