How many terms of the A.P. 25, 22, 19, …. are needed to give the sum 116 ? Also find the last term.

How many terms of the A.P. 24, 21, 18, … must be taken so that the sum is 78 ? Explain the double answer.

In an A.P., the fourth and sixth terms are 8 and 14 respectively. Find the :

(i) first term

(ii) common difference

(iii) sum of first 20 terms

Find the sum of first 51 terms of the A.P. whose second and third terms are 14 and 18 respectively.