Let's first calculate the amount of money the man receives from selling 1/3rd of the land and 2/5ths of the land.
1/3 of the land is (1/3) * 300000 = 100000, and he sells it at a loss of 20%, which means he sells it for 100000 - (20/100) * 100000 = 80000.
2/5 of the land is (2/5) * 300000 = 120000, and he sells it at a gain of 25%, which means he sells it for 120000 + (25/100) * 120000 = 150000.
The total money he receives from selling 1/3rd and 2/5ths of the land is 80000 + 150000 = 230000.
He bought the land for Rs. 300000 and received Rs. 230000 from selling a portion of it. So, he still has Rs. 70000 worth of land left.
To make a profit of 10%, he needs to sell the remaining land for 300000 + (10/100) * 300000 = Rs. 330000.
The remaining land is worth Rs. 70000, so he needs to sell it for Rs. 330000 - Rs. 230000 = Rs. 100000.
Therefore, he must sell the remaining land for Rs. 100000 to make an overall profit of 10%.