The average age of Sushanth, Krish, and Rishi is 43 years. The average age of Sushanth, Rishi, and Rohit is 49 years. If Rohit is 54 years old, what is Krish's present age (in years)?

Introduction:
This problem tests comparing two averages where two people are common in both groups. When two averages are given, convert each average into a total sum. Because Sushanth and Rishi appear in both groups, subtracting the totals removes the common part and isolates the third person's age difference. Then, using Rohit's known age, we can find Krish's age directly.

Given Data / Assumptions:

• Average(Sushanth, Krish, Rishi) = 43
• Average(Sushanth, Rishi, Rohit) = 49
• Rohit = 54
• All ages are present ages in years

Concept / Approach:
Total of 3 persons = average * 3. Use the two totals to find (Sushanth + Rishi) and then substitute into the first total to get Krish.

Step-by-Step Solution:
Sushanth + Krish + Rishi = 43 * 3 = 129Sushanth + Rishi + Rohit = 49 * 3 = 147Sushanth + Rishi = 147 - 54 = 93Krish = 129 - 93 = 36

Verification / Alternative check:
If Krish is 36, then Sushanth + Rishi = 93 makes the first group total 93 + 36 = 129, average 129/3 = 43 which matches. Second group total is 93 + 54 = 147, average 147/3 = 49 which also matches.

Why Other Options Are Wrong:
34 years and 26 years: come from subtracting averages directly instead of totals.24 years: ignores Rohit's value in the second total.38 years: would change the first average away from 43.

Common Pitfalls:
Subtracting 49 - 43 and treating it as a direct age difference.Forgetting to multiply the averages by 3.Assuming Rohit is part of the first group by mistake.

Final Answer:
36 years