Data Sufficiency — Year of birth: determine Rahul’s birth year Question: In which year was Rahul born? Statements: I. Rahul at present is 25 years younger than his mother. II. Rahul's brother, born in 1964, is 35 years younger than his mother. Choose the correct sufficiency conclusion.

Analyze each statement

• I alone: Gives only the age difference (Mother − Rahul = 25). Without the mother's birth year/age, Rahul's year of birth is indeterminate.
• II alone: From “brother was born in 1964 and is 35 years younger than mother” ⇒ Mother's birth year = 1964 − 35 = 1929. But Rahul's age difference from mother is unknown, so Rahul's birth year is still indeterminate.

Together
With I + II, one could find Rahul's year (1929 + 25 = 1954). However, neither statement alone is sufficient by itself.

Final Sufficiency Choice
Neither I nor II is sufficient.