Data sufficiency: how old is Ravi? — Aptitude Question
Data sufficiency: how old is Ravi?: Question: How old is Ravi? Statement I: Ravi is 5 years older than his brother. Answer and worked solution on CodeKairo.
- Topic: Mathematical Reasoning
- Section: Logical Reasoning
- Difficulty: Medium
- Time target: 75 seconds
Question
Question: How old is Ravi?
Statement I: Ravi is 5 years older than his brother. Statement II: Ravi's brother will be 20 next year.
Which statements are needed?
Options
- I alone is enough
- II alone is enough
- Both together are needed
- Even both are not enough
Show the answer and the worked solution
Correct answer: C. Both together are needed
Worked solution
- I alone: Ravi = brother + 5, but the brother's age is unknown. Not enough.
- II alone: the brother is 19 now, but Ravi's relation to him is unknown. Not enough.
- Together: brother is 19, so Ravi is 24. Both together are needed.
Answer: Both together are needed.
The idea
Test each statement alone before testing them together, and never carry information from one into the other. Answer the sufficiency question, not the arithmetic one.
Shortcut. Ask what each statement fixes: I gives only a gap and II only the brother's age; a gap plus one age fixes Ravi (19 + 5).
Common trap. "II alone is enough" — it pins the brother at 19, and a hurried reader forgets the question asks for Ravi's age.