Q7 of 89 Page 45

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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