Robi invests Tk. 40,000/- in a car wash center and starts a business. After 4 months, Rasel joins the business with an investment of Tk.50,000. At the end of the year, they make a profit of Tk. 1,87,000/-. What will be Rasel's share in this profit?

We know,
The ratio of Investment x Time = Ratio of Profit
∴ (A's investment x Time) : (B's investment x Time) = Profit of A : Profit of B

∴ (Robi's Investment x Time) : (Rasel's Investment x Time) = Robi's Profit : Rasel's Profit
∴ 40000 x 12 : 50000 x 8 = Robi's Profit : Rasel's Profit
∴ Robi's Profit : Rasel's Profit = 4,80,000 : 4,00,000 = 6:5
∴ Rasel's profit = (5/11) × 187000 = Tk. 85000