Answer : 4. "8 months"
Explanation :

Answer: D) 8 months Explanation: Let the total Profit be Z.Ramu's profit share is 2/3 of profit (i.e 2Z/3)Ravi's profit is (Z-2Z/3) =Z/3Hence the profit ratio is , Ravi : Ramu = Z/3 : 2Z/3 = 1:2 Let total Capital be Rs.X and Ramu has contributed for Y months.Since Ramu's profit share is 2/3, his invest share will be 2/3 in capital. Ravi's invest for 16 months / Ramu's invest for Y months = Ravi's profit share / Ramu's profit sharei.e. (X/6 x 16) / (2X/3 x Y) = 1/2 Solving the above equation, we get Y = 8.So Ramu's money has been used for 8 months.