Ten years ago, Sachin was twice as old as Ajay was then. If Sachin will be 40 years old ten years from now, how old is Ajay today?

Introduction / Context:
Combine past-time multiplicative information with a future-time absolute age to deduce present ages.

Given Data / Assumptions:

• Sachin in 10 years = 40 ⇒ Sachin now = 30
• 10 years ago Sachin = 20, and at that time Sachin = 2 × (Ajay then)

Concept / Approach:
From the past relationship, find Ajay's past age, then add the elapsed time to get Ajay's present age.

Step-by-Step Solution:

Verification / Alternative check:
Check: Ten years ago Ajay 10, Sachin 20, twice relation holds; in 10 years Sachin 40, consistent.

Why Other Options Are Wrong:
10, 15, 30 contradict either the past twice relation or Sachin’s future age.

Common Pitfalls:
Forgetting to convert the future age into present age before using the past condition.

Final Answer:
20 years.