Since the 22nd term is 13 terms after the 9th term,
55 = 29 + 13d
Now you can find d and a, and then use your sum formula:
S30 = 30/2 (2a + 29d)
the 9th and 22nd term of an a.p are 29 and 55 respectively find the sum of its 30 terms.
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2 answers