If 7 times the 7th term of an AP is equal to 11 times its 11th term, then its 18th term will be


Let a and d be first term and common difference respectively


According to the question,


7a7 = 11a11


As we know, nth term of an AP is


an = a + (n - 1)d


where a = first term


an is nth term


d is the common difference


we have


7(a + 6d) = 11(a + 10d)


7a + 42d = 11a + 110d


4a + 68d = 0


a + 17d = 0


a18 = 0


18th term of AP is 0

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