RRB RPF RPSF SI and CONS Model Papers 3 with solutions

(d) Let R, G and B represent the number of balls in red, green and blue boxes respectively.
Then, R + G + B = 108 ...(i),
G + R = 2B ...(ii)
B = 2R ...(iii)
From (ii) and (iii), we have G + R = 2 × 2R = 4R or G = 3R.
Putting G = 3R and B = 2R in (i), we get:
R + 3R + 2R = 108⇒ 6R = 108 ⇒R = 18.
Therefore Number of balls in green box = G = 3R = (3 × 18) = 54.