Question

Kanika was given her pocket money on Jan $1^{st}$, 2008. She puts Re 1 on Day 1, Rs 2 on Day 2, Rs 3 on Day 3, and continued doing so till the end of the month,from this money into her piggy bank. She also spent Rs 204 of her pocket money, and found that at the end of the month she still had Rs 100 with her. How much was her pocket money for the month?

Answer 1

Clearly, money put by kanika in piggy bank form an AP as $1,2,3,...,31$
Sum of money after end of month$=\frac{31}{2}(1+31)=31\times 16=496$ (Sum of AP whose first and last term is known.)
Kanika total pocket money$=496+204+100=800$