If the ratio of the sum of first terms of two APs is , find the ratio of their 9th terms.

Answer and explanation

Correct answer: D.

  1. Step 1: .
  2. Step 2: For the 9th term, we need , so .
  3. Step 3: Substitute : .
Answer
.
Why not the others: is the unreduced fraction form; uses directly; and makes an arithmetic subtraction slip.

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