Problems on Ages – Data Sufficiency 2
Each of the questions given below consists of a question followed by three statements. You have to study the question and the statements and decide which of the statement(s) is/are necessary to answer the question.
2. 


Answer: Option A Explanation: I. Let Ravi’s present age be x years. Then, his father’s present age = 2x years. II. After 5 years, III. Ravi is younger than his brother. From I and II, we get Thus, I and II together give the answer. Clearly, III is redundant. 
3. 


Answer: Option E Explanation: I. Let the present ages of Tanya and Rahul be 3x years and 4x years. II. After 5 years, (Tanya’s age) : (Rahul’s age) = 4 : 5. III. (Rahul’s age) = (Tanya’s age) + 5. From I and II, we get From I and III, we get 4x = 3x + 5. This gives x. From III : Let Tanya’s present age be t years. Then Rahul’s present age = (t + 5) years. Thus, from II and III, we get : Thus, II and III give the answer. 
Check this also:
 Problems on Ages – Data Sufficiency 1
 Problems on Ages – Data Sufficiency 3
 Problem on Ages – Aptitude test