John invested P100,000 at an interest of 9% compounded quarterly. How many years should John invest the money to receive a compound interest of P50,0000? 

2. An engineer decided to put up a trust fund for her daughter with the condition that his daughter will receive the earnings of the 400,000 at the end of every 4 years until the 20th year when his daughter will receive P400,000 earning including also the money initially deposited. If the bank guaranteed a 16% interest per year, what is the principal worth to meet such condition? 

3. The cost for maintaining a car cost as follows: 2 years- P20,000 4 years- P40,000 8 years- 80,0000. Solve for the semi-annual amount for the car if the interest is 10% compounded annually.