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If the 5th term of an AP is 1 10 and its 10 th term is 1 5 , then what is the sum of first 50 terms?

Options

  1. A25
  2. B25.5
  3. C26
  4. D26.5

Correct answer

B. 25.5

Step-by-step solution

a₅= 1 10 a+4 d= 1 10 ...(i) a ₁₀= 1 5 a +9 ~d = 1 5 ...(ii) from (i) and (ii), we get a = 1 50 and d = 1 50 S ₅₀= 50 2 [ 2 50 + 49 50 ]= 50 2 51 50 =25.5

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