If the 2nd terms of an AP is 13 and 5th term is 25, what is its 7th term?


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


a2 = a + d = 13 …..(1)


a5 = a + 4d = 25 ……(2)


Solving 1 and 2


From 1 we have


a = 13 - d


using this in 2, we have


13 - d + 4d = 25


13 + 3d = 25


3d = 12


d = 4


a = 13 - 4 = 9


a7 = a + 6d


= 9 + 6(4)


= 9 + 24 = 33

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