**CBSE NCERT Solutions Chapter 5 Arithmetic Progressions Exercise 5.2 Question 1**

**(1) Find the missing variable from a, d, n and , where a is the first term, d is the common difference and is the nth term of AP.**

**(i) a= 7, d = 3, n = 8**

**(ii) a = -18, n= 10, **

**(iii) d = -3, n = 18,**

**(iv) a = -18.9, d = 2.5, **

**(v) a = 3.5, d = 0, n = 105**

**Solution (i)**

a= 7, d = 3, n = 8

We need to find ** here.**

Using formula and putting values of a, d and n, we get

**Solution (ii)**

a = -18, n= 10,

We need to find **d** here.

Using formula and putting values of a, and n, we get

0 = -18 + (10 - 1)d

**Solution (iii) **

d = -3, n = 18,

We need to find **a** here.

Using formula and putting values of d, and n, we get

-5 = a + (18-1)(-3)

**Solution (iv)**

a = -18.9, d = 2.5,

We need to find **n** here.

Using formula and putting values of d, and a, we get

3.6 = -18.9 + (n-1) (2.5)

**Solution (v)**

a = 3.5, d = 0, n = 105

We need to find ** here.**

Using formula and putting values of d, n and a, we get