Question

Kanika was given her pocket money on $1^{st}$ Jan,$2008$. She puts $Rs1$ on Day $1$, $Rs2$ on Day $2$, $Rs3$ on Day $3$, and continued on doing so till the end of the month, from this money into her piggy bank. She also spent $Rs204$ of her pocket money, and was found that at the end of the month she still has $Rs100$ with her. How much money was her pocket money for the month?

Answer 1

Total pocket Money $=$ Money in piggy bank $+$ expenses $+$ left

$=(1+2+3+...+31)+204+100$

$=\frac{31\times 32}{2}+204+100$

$=31\times 16+304$

$=496\times 116+304$

$=800Rs.$