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      Question

      Average of 17 numbers is 81. If the average of the first

      six and last eight numbers is 91.5 and 71.5 respectively, and if the ninth number is 20% more than the eighth number and the tenth number is (50/9)% less than the ninth number, then find the ninth number.
      A 50.7 Correct Answer Incorrect Answer
      B 91.8 Correct Answer Incorrect Answer
      C 11.45 Correct Answer Incorrect Answer
      D 37.9 Correct Answer Incorrect Answer
      E None of these Correct Answer Incorrect Answer

      Solution

      ATQ, Let the eighth number be 10x. So, the ninth number = 1.20 ร— 10x = 12x. Tenth number = 850/9 ร— 1/100 ร— 12x = 34x/3. So, 10x + 12x + 34x/3 = 81 ร— 17 โ€“ 6 ร— 91.5 โ€“ 8 ร— 71.5 = 255. Or, 100x/3 = 255. Or, x = 7.65. So, the ninth number = 12 ร— 7.65 = 91.8.

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