The sum of 15 terms of an AP (Arithmetic Progression) series is 600 and the difference between any two consecutive terms is 5. Find the first term of the series.

Question

Question

This question was previously asked in

UGC NET Paper 1: Held on 16th Mar 2023 Shift 1

Answer 1

Formula used:

S = n/2 × [2a + (n - 1)d]

Where:

n is the number of terms,

a is the first term,

d is the common difference between terms.

Here, n = 15 (number of terms),

S = 600 (sum of the terms), and

d = 5 (common difference).

Calculation:

Substituting these values into the formula, we get:

600 = 15/2 × [2a + (15 - 1)5]

⇒ 600 = 7.5 × (2a + 70)

⇒ 600 = 15a + 525

⇒ 75 = 15a

⇒ a = 75/15

⇒ a = 5

So, the first term of the series is 5.

Therefore, the answer is 5.

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