Two persons Choton and Billal started a business in which Choton invested Tk. 50000, Billal invested Tk. 80000, after 4 months Robiul joined them with a certain amount. At the end of the year, a total profit of Tk. 40000 was recorded. Robiul's share in the profit was Tk. 15000, then find Robiul's investment in the business.

Question: Two persons Choton and Billal started a business in which Choton invested Tk. 50000, Billal invested Tk. 80000, after 4 months Robiul joined them with a certain amount. At the end of the year, a total profit of Tk. 40000 was recorded. Robiul's share in the profit was Tk. 15000, then find Robiul's investment in the business.Solution:Let,Robiul's investment in the business be Tk. 1000xProfit ratio of Choton, Billal and Robiul = (50000 × 12) : (80000 × 12) : {1000x × (12 - 4)}= 75 : 120 : xTotal profit = 75 + 120 + x = 195 + xRobiul's share in profit = xATQ,(195 + x)/x = 40000/15000⇒ (195 + x)/x = 8/3⇒ 3(195 + x) = 8x⇒ 585 + 3x = 8x⇒ 5x = 585⇒ x = 117Investment by Robiul = 1000 × 117 = Tk. 117000