RRB Group-D Model Paper 17 with answers for online practice

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