Arithmetic Prog...

If fourth therm of an $$A.P$$ is thrice its first term and seventh term is one less than the twice of third term, then its common difference is ?

Sum of first $$n$$ natural numbers is $$S_{1}$$, sum of first $$n$$ odd natural numbers is $$S_{2}$$, and sum of first $$n$$ even numbers is $$S_{3}$$. Then $$S_{1}:S_{2}:S_{3}$$=

Sum of the first $$n$$ terms of an A.P. having first term $$a$$ and last term $$\ell$$ is ____

If the first, second and last term of an $$A.P.$$ are $$a,\ b$$ and $$2a$$ respectively. then its sum is

If the ratio of $${n^{th}}$$ terms of two A.P.'s is $$\left( {2n + 8} \right):\left( {5n - 3} \right)$$, then the ratio of the sums of their $$n$$ terms is 

A man saved Rs. $$200$$ in each of the first three months of his service. In each of the subsequent months his saving increases by Rs. $$40$$ more than the saving of immediately previous month. His total saving from the start of service will be Rs. $$11040$$ after.

For the A.P. if $$a = 7$$ and $$d = 2.5 ,$$ then $$t _ { 12 } = ?$$

Three  numbers are in $$AP$$ such that their sum is $$18$$ and sum of their squares is $$158$$. The greatest number among them is

Find the sum of $$2,4,6,8,,,........2n$$

The $$27^{th}$$ term of AP $$7,9,11,13,15,17,19,\ldots$$ is