Ankit starts a partnership with an investment of Rs. 4320. After five months Sunil joined him with an investment of Rs. 3600. Again after some time profit was distributed among them in ratio of 36 : 25. Find the investment time of Ankit.

Profit ratio equals investment ratio when time is accounted for. Ankit invested Rs. 4320 for T months, Sunil invested Rs. 3600 for (T-5) months. The ratio is (4320 × T) : (3600 × (T-5)) = 36 : 25. Simplifying: 4320T / 3600(T-5) = 36/25. Cross-multiplying: 4320T × 25 = 36 × 3600(T-5). This gives 108000T = 129600(T-5). Solving: 108000T = 129600T - 648000, so 21600T = 648000, giving T = 30 months.