n^th term of a sequence is a + nb. Find a₄ - a₃.

Sum of first 11 terms of an AP is 220. Then the 6^th term is  

Sum of first 10 natural numbers is

If the common difference of an A.P is d, then a₃ - a₁ equal to

The middle term of the AP 1, 8, 15....... 505 is

The number of odd integers between 8 and 80 is 

The number of even numbers between 1 and 199 is

The n^th term of the sequence 3, 6, 9.... is 

Which term of the A.P 21, 18, 15, ..... is 0?

Value of a_{m + n} + a_{m - n} =