Correct Answer - Option 2 : 1/5

**Given:**

The sum of the first 25 terms = 305

**Formula used:**

T_{n} = a + (n – 1) d

S_{n }= n/2 × [2a + (n – 1) d], where a is the first term. n is number of terms and d = common difference.

**Calculation: **

T_{5} = a + (5 – 1) d

⇒ T_{5} = a + 4d ---- (1)

And T_{9} = a + 8d ---- (2)

∴ T_{9} – T_{5} = 4

⇒ a + 8d – a – 4d = 4

⇒ 4d = 4

⇒ d = 1

According to question

⇒ 305 = 25/2 × [2a + (25 – 1) 1]

⇒ 122 = 10a + 5(24)

⇒ 122 = 10a + 120

⇒ 10a = 122 – 120

⇒ 10a = 2

⇒ a = 2/10

∴ a = 1/5