Siblings with fixed gap – Nikhil is 8 years younger than Rohan. How old will Rohan be when he is exactly twice as old as Nikhil?
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A4 years
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B6 years
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C8 years
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D16 years
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E18 years
Answer
Correct Answer: 16 years
Explanation
Introduction / Context:We are asked for the age Rohan will be at the moment he is twice Nikhil, given a constant present gap. Modeling “t years from now” for both brothers and equating produces a single linear equation in t that directly yields Rohan’s target age.
Given Data / Assumptions:
- Nikhil = Rohan − 8 (present ages).
- We want t such that Rohan + t = 2(Nikhil + t).
Concept / Approach:Substitute Nikhil in terms of Rohan, solve for the calendar time t, then compute Rohan’s age at that time.
Step-by-Step Solution:R + t = 2((R − 8) + t) = 2R − 16 + 2t.Bring terms together: R + t − 2R + 16 − 2t = 0 ⇒ −R − t + 16 = 0 ⇒ R + t = 16.Therefore, when the condition holds, Rohan will be 16 years old.
Verification / Alternative check:If Rohan is 16, Nikhil is 8 (because the gap is 8). 16 = 2 × 8, so the condition is satisfied.
Why Other Options Are Wrong:They do not meet the 2× condition alongside the fixed 8-year gap.
Common Pitfalls:Solving for t and reporting t instead of Rohan’s age at that time. The question explicitly asks for Rohan’s age.
Final Answer:16 years