Question

12. Under usual notations in an AP if 2a = d, then the ratio of the sum to first 11 terms and
the sum to first 5 term =​

Answer 1

Answer:

121/25

Step-by-step explanation:

If 2a = d

S(11)=11/2[2a+(n-1)d] ...........(n=11)

      =11/2[d+10d]

      =11/2(11d)

      =121d/2

S(5)=5/2[d+4d]...........(n=5)

      =5/2(5d)

      =25d/2

Ratio=> (121d/2) / (25d/2)

        =>121/25

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