X and Y can do a piece of work in 20 and 40 days respectively. If they work together, how long will they take to finish the work?

🧠 Explanation (Math):

Given: X in 20 days, Y in 40 days; together time?
Step 1: Rates: X = 1/20, Y = 1/40 (work/day)
Step 2: Combined rate = 1/20 + 1/40 = 3/40
Step 3: Time = 1 ÷ (3/40) = 40/3 days
Final Answer: 10 days