First of all if I get a 100 rupee not legally from my parent , then I will plan it according my strategy. First of all I will make it white money according to our Islamic law of helping poor.
Therefore I will give 2.5% of 100 ie Rs 2.50 to a poor needy student. After that I will save at least 40% of the rest for my future need. That means I will kep Rs 39.00 (40%x97.50) as saving. The rest 50 rupees (97.5-39=58.50) will be for my current expenditure.
So it is my basic financial rule. Now I will expend this money by making a priority list of my requirement. As the money is small therefore I will use it for buying small needful things.
My priority list of expenditure is : pen, pencil, scale, story book, branded chocolates, and sweets. I like having varieties of pens of different colours. So I will buy pens. As the cost of pen is around 8 rupees . Therefore the three pen will cost around Rs. 24.