Out of 30,000 rupees received, the trust spends half for medical and education care.
Hence, the amount deposited in private bank is the remaining half = 15,000 rupees.
The trust charges 2% of the money spent for medical and educational care.
Hence, the earning of the trust from the above charges is 2% of 15,000 = 15,000 * 2/100 = 300 rupees.
Hence, to get a total of 1800 rupess per month, the trust should receive the remaining 1800-300 = 1500/ rupees from the bank.
Let the interest rate obtained from the bank be R%.
Hence R% of 15,000 = 1500
15,000 * R/100 = 1500
Hence, the trust should get an interest of 10% per month from the bank.