Is $1^{11}+2^{11}+3^{11}+4^{11}$ divisible by $5?$ Explain.

Find the number of rectangles of the given figure?

Rahul’s father wants to deposit some amount of money every year on the day of Rahul’s birthday. On his $1^{\mathrm{st}}$ birthday $Rs.100,$ on his $2^{\mathrm{nd}}$ birthday $\mathrm{Rs}.300,$ on his $3rd$ birthday $Rs.600,$ on his $4^{\mathrm{th}}$ birthday $Rs.1000$ and so on. What is the amount deposited by his father on Rahul’s $15th$ birthday.

Find the sum of integers from $1$ to $100$ which are divisible by $2$ or $5.$

Find the sum of integers from $11$ to $1000$ which are divisible by $3.$