2. Questions Bank
  3. 11th Class
  4. Mathematics
  5. Sequence and Series

11th Class Mathematics Sequence and Series Question Bank Sequence and Series (A.P., G.P. and H.P.)

  • question_answer
    Which term of the AP 3, 8, 13, 18,..........is 78?

    A)  10th                             

    B)  12th                

    C)  14th                             

    D)  16th

    Correct Answer: D

    Solution :

    (d): Let nth term be 78. Given, 3, 8, 13, 18........are in AP. First term, a = 3, common difference, d = 8 ? 3 = 5 \[\because \] nth term \[{{a}_{n}}=78\] \[\therefore \] \[a+(n-1)d=78\Rightarrow 3+(n-1)5=78\] \[\Rightarrow \]\[(n-1)5=78-3\Rightarrow 5(n-1)=75\] \[\Rightarrow \]\[n-1=15\Rightarrow n=15+1\Rightarrow n=16\] Thus, 78 term is 16th.


You need to login to perform this action.
You will be redirected in 3 sec spinner