If the $n^{th}$ terms of two $A.P.$'s are $3n + 8$ and $7n + 15$,then the ratio of their $12^{th}$ terms will be:

If the sides of a right-angled triangle are in an arithmetic progression,then they are in the ratio of.........

If $p(\frac{1}{q}+\frac{1}{r}), q(\frac{1}{r}+\frac{1}{p}), r(\frac{1}{p}+\frac{1}{q})$ are in $AP$,then $p, q, r$:

The natural numbers are arranged in rows as follows:
$1$
$2, 3$
$4, 5, 6$
$7, 8, 9, 10$
$. . .$
What is the sum of the numbers in the $n^{th}$ row?

The sum of all natural numbers between $1$ and $100$ which are multiples of $3$ is

If the sum of the first $2n$ terms of the arithmetic progression $2, 5, 8, \dots$ is equal to the sum of the first $n$ terms of the arithmetic progression $57, 59, 61, \dots$,then $n = \dots$