C and D invest in a business in a ratio of 4:5. If 10% of the total profit goes to charity and D's share is Rs.900 after the donation, what is the total profit?

Let the total profit be P. Since 10% is donated to charity, the remaining profit that is shared between C and D is 90% of P. Remaining profit = P×90/100 = 0.9P D's share is greater than C's since they invested in a ratio of 4:5. Therefore, for every 9 parts of the profit, D gets 5 parts. First, let's find out what 1 part is worth: D's share = (5/9) × 0.9P = 0.5P Given that D's share after the donation is 900: 0.5P - 900 P = 900/0.5 P = 1800 So, the total profit before the donation to charity is 1800Rs.