Shortcut Trick Present ratio (Ritika : Vipul) = 3 : 1 (Difference = 2 units) Ratio after 7 years = 2 : 1 (Difference = 1 unit) Make differences equal: Multiply second ratio by 2 ⇒ 4 : 2 Ratio change: 3 → 4 (Ritika) and 1 → 2 (Vipul) ⇒ 1 unit = 7 years Ritika's present age = 3 units = 3 × 7 = 21 years ∴ The correct answer is 21 years. Alternate Method Given: Present age of Vipul = x Present age of Ritika = 3x Calculations: ⇒ After 7 years, Ritika's age = 3x + 7 ⇒ After 7 years, Vipul's age = x + 7 ⇒ According to the question: (3x + 7) = 2 × (x + 7) ⇒ 3x + 7 = 2x + 14 ⇒ 3x − 2x = 14 − 7 ⇒ x = 7 ⇒ Ritika's present age = 3x = 3 × 7 = 21 years ∴ The correct answer is 21 years. Related Concepts: Age Ratio Concept The difference between the ages of two persons remains constant regardless of the number of years passed. Linear Equation in One Variable Problems involving ages are typically solved by expressing all ages in terms of a single variable (usually the present age) and forming an equation based on the given condition.