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The sum of 15 terms of an arithmetic progression is 600 and the common difference between consecutive terms is 5. Find the first term of the series.

A5 ✓ Correct
B7
C8
D9
Correct answer: (A) 5
Explanation

The first term is 5.

sum formula: S = n/2 x (2a + (n-1)d).

600 = 15/2 x (2a + 14 x 5).

80 = 2a + 70.

2a = 10, so a = 5.

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