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Now, subtract the equation (i) from (ii) we get,

7d = 35

⇒ d =

⇒ d = 5

Substitute the value of d = 5 in the equation (i) we get,

a + 4 × 5 = 30

⇒ a + 20 = 30

⇒ a = 30 - 20

⇒ a = 10

Therefore, the first term of the Arithmetic Progression is 10 and common difference of
the Arithmetic Progression is 5.

Now, sum of the first 26 terms of an Arithmetic Progression S2626 = 262262[2 × 10 +
(26 - 1) × 5], [Using the Sum of the First n Terms of an Arithmetic Progression

S n = [2a + (n - 1)d]

= 13 [20 + 25 × 5]

= 13 [20 + 125]

= 13 [145]

= 1885

Sum of n terms of an AP-

S = [2a + (n - 1)d]

where a = first term, d = common difference

Or, S = [a + l], where l = last term = a + (n - 1)d

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