The Fifth terms Of An A.P. Is 1 Whereas Its 31st Term Is – 77. Find Its 20th Term And Sum Of Its First Fifteen Terms. Also Find Which Term Of The Series Will Be  –17 And Sum Of How Many Terms Will Be 20.

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Question

The fifth terms of an A.P. is 1 whereas its 31st term is – 77. Find its 20th term and sum of its first fifteen terms. Also find which term of the series will be  –17 and sum of how many terms will be 20.

Solution

Correct option is

n = 8

        .  

Solving the above two, we get 

            a = 13 and d = –3.                … (i)   

         

              

Let    Tn = –17. Then a + (n – 1)d = –17      

        

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The value of n cannot be fractional.

SIMILAR QUESTIONS

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Q3

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Q5

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Q8

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Q9

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