Which number is the next in the series 1/5, 1/9, 1/13, 1/17?

🧠 Explanation (Math):

Given: Series 1/5, 1/9, 1/13, 1/17, ?
Step 1: Denominators increase by 4
Step 2: Next denominator = 21 ⇒ next term = 1/21
Final Answer: 1/21