A and B started a business in a partnership investing the money in the ratio 2 : 5. C joined them after 3 months with an amount equal to (\frac{4}{5})th of B. What is the total profit after the end of the year, if A got Rs.16800 as his share?

Investment ratio A:B = 2:5. Let A = 2x, B = 5x. C joins after 3 months with amount = 4/5 of B = 4x. Equivalent investments for 1 year: A = 12×2x = 24x, B = 12×5x = 60x, C = 9×4x = 36x. Ratio A:B:C = 24:60:36 = 2:5:3. A's share is 2/(2+5+3) = 2/10 = 1/5. If A gets Rs 16800 (1/5 of profit), total profit = 16800 × 5 = Rs 84000.