# Find the Sum of the Following Arithmetic Progressions: a + B, a − B, a − 3b, ... to 22 Terms - Mathematics

Find the sum of the following arithmetic progressions:

a + b, a − b, a − 3b, ... to 22 terms

#### Solution

In the given problem, we need to find the sum of terms for different arithmetic progressions. So, here we use the following formula for the sum of n terms of an A.P.,

S_n = n/2 [2a +_ (n -1)d]

Where; a = first term for the given A.P.

d = common difference of the given A.P.

= number of terms

a + b, a − b, a − 3b, ... to 22 terms]

Common difference of the A.P. (d) = a_2 - a_1

= (a - b) -(a + b)

= a - b - a - b

= -2b

Number of terms (n) = 22

The first term for the given A.P. (a) = a + b

So, using the formula we get,

S_22 = 22/2 [2(a + b) + (22- 1)(-2b)]

= (11)[2a + 2b + (21)(-2b)]

= (11)[2a + 2b - 42b]

= 22a - 440b

Therefore the sum of first 22 terms for the give A.P is 22a - 440b

Is there an error in this question or solution?

#### APPEARS IN

RD Sharma Class 10 Maths
Chapter 5 Arithmetic Progression
Exercise 5.6 | Q 1.5 | Page 30