Assume that the person decided to go on for a tour for 'x' days. Now, he has a total of 360 rupees for his daily expenses. This means he spends 360/x per day. Suppose he extends his programme by 4 days his daily expenses reduce to (360/x - 3) rupees per day. Now the number of days he spends on tour are x+4 days with 360/x - 3 rupees to spend per day and the total amount of money be had is 360.
We have our equation (x+4)(360/x - 3)=360
By simplifying this you have x²+4x-480=0
Using quadratic formula you will have the answer to be 20 days