Arithmetic Prog...

The sum of the first $$100$$ natural numbers is

Find the sum of all odd natural numbers from 1 to 150.

If the following sequence is an arithmetic progression, find its general term. 
-5, 2, 9, 16, 23, 30, .......... is 

Find $$S_{10}$$, if a = 6 and d = 3.

How many terms of the sequence $$18, 16, 14,....$$ should be taken so that their sum is zero?

How many terms are there in the A.P.: $$-1,\displaystyle\frac{-5}{6},\displaystyle-\frac{2}{3},\displaystyle\frac{-1}{2}, ....., \displaystyle\frac{10}{3}$$ ?

Find the sum of $$7 + 10\dfrac{1}{2} + 14+...+84$$.

The fourth term of an A.P. is $$4$$. Then the sum of the first $$7$$ terms is ?

Write the arithmetic progression when first term $$a = -1.5$$ and common difference $$d = -0.5$$.

Find the $$18^{th}$$ term of the A.P., $$\sqrt{2}, 3\sqrt{2}, 5\sqrt{2}$$.....