Find the sum of two-digit natural numbers divisible by $6$.

$200$ logs are stacked in the following manner: $20$ logs in the bottom row,$19$ in the next row,$18$ in the row next to it and so on (see Figure). In how many rows are the $200$ logs placed and how many logs are in the top row?

In an $AP$,if $S_{n} = n(4n + 1)$,find the $AP$.

If the sum of the first $n$ terms of an $AP$ is $4n - n^2$,what is the first term (that is $S_1$)? What is the sum of first two terms? What is the second term? Similarly,find the $3^{rd}$,the $10^{th}$ and the $n^{th}$ terms.

$A$ person has to clear a debt of $Rs. 3250$ by monthly instalments. In the first month he has to pay $Rs. 20$ and then onwards every instalment is $Rs. 15$ more than the previous instalment. How long will it take to clear the debt?

$Rs. 280$ is to be distributed among four prizes. If the prize amount in each successive prize reduces by $Rs. 20$,find the amounts paid in those prizes.