The first term of an A.P. is 5, the common difference is 3 and the last term is 80; find the number of terms.

Is -150 a term of the A.P. ?

How many terms are there in the A.P.?

(i)

(ii)

(iii)

(iv)

The 6^th and 17^th terms of an A.P. are 19 and 41 respectively, find the 40^th term.

If 9^th term of an A.P. is zero, prove that its 29^th term is double the 19^th term.