Q. 54.1( 14 Votes )

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Answer :

Given: a2 = 13


a5 = 25


To find: a7


Formula Used: nth term of an AP is:


an = a + (n - 1) d


Explanation:


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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