In an A.P, S1, S2, S3 are sum of first 15, 30, 45 terms respectively. If S3 = 300, S2 = 150 find S1.
50
For an A.P., if S1, S2, S3 are the sums of the first n, 2n, 3n terms, then S3 = 3(S2 - S1).
300 = 3(150 - S1)
150 - S1 = 100
S1 = 50
Check: blocks of 15 terms have sums S1 = 50, S2 - S1 = 100, S3 - S2 = 150, which form an A.P. with common difference 50, as required.
Hence, 50.
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A series is given with one term wrong. Select that wrong term from the given alternatives.
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