1. Find (a) the 15 th term, (b) the sum of the first 15 terms.

for the following sequences

(i) 12,17,22,...

(ii) 4,10,16,....

2. Find the number of terms in the following sequences

a) 5,11,17,...,83

b) 4,8,12,...,40

3. The 5 th and 13 th terms of an arithmetic sequence are 25 and 65 respectively. Find the first term and the common difference of the arithmetic sequence.

4. An arithmetic sequence is given as follows: -20,-15,-10,...,175.

a) Find the number of terms in the sequence.

b) Find the sum of the last 20 terms.

5. The first term and common difference of an arithmetic sequence are -9 and 8 respectively. If the sum of the first n term is 1340, find n