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The average of nine numbers is 60, that of the first five numbers is 55 and the next three is 65. The ninth number is 10 less than the tenth number. Then, tenth number is -

Options

  1. A80
  2. B70
  3. C75
  4. D85

Correct answer

A. 80

Step-by-step solution

Given: Average of nine numbers (=60 ) Average of first five numbers (=55 ) and average of next three numbers (=65 ) Tenth number (= ) Ninth number +10 Concept used: Average (= ) Total sum of all numbers (/ ) (Count of the numbers) Calculation: The sum of nine numbers (=60 9=540 ) The sum of the first five numbers (=55 5=275 ) The sum of the next three numbers (=65 3=195 ) Ninth number (=(540-275-195)=(540-470)=70 ) ( ) Tenth number (=70+10=80 )

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