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

**5.** ** The first term of an AP is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.**

**Solution:**

First term = a = 5

Last term =

**Applying formula**, to find sum of n terms of AP, **we get**

**Applying formula,** to find sum of n terms of AP and putting value of n, we get