**CBSE NCERT Solutions Chapter 5 Arithmetic Progressions Exercise 5.3 Question 11**

**11. If the sum of the first n terms of an AP is , what is the first term (that is S1)? What is the sum of first two terms? What is the second term? Similarly, find the 3rd, the 10th and the nth terms.**

**Solution:**

It is given that the sum of n terms of an AP is equal to .

It means

Lets calculate and using .

First term **(1)**

Lets find common difference now.

We can write any AP in the form of general terms like a , a+d, a + 2d, ...

We have calculated that sum of first two terms is equal to 4 i.e

Therefore, we can say that

Putting value of from equation **(1), **we get

**Using formula** , to find nth term of arithmetic progression, **we can say that**

**Second term of AP = = **

**Third term of AP = = **

**Tenth term of AP = = **

**nth term of AP = = **