Tips & Tricks Let the initial number of red balls be 2x and initial number of blue balls be 3x When 2 blue balls were added, New Ratio = 2x : (3x + 2) = 3 : 5 ⇒ 5 × 2x = 3 × (3x + 2) ⇒ 10x = 9x + 6 ⇒ 10x - 9x = 6 ⇒ x = 6 Number of red balls in box = 2 × 6 ∴ Number of red balls in the box is 12