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The average of n numbers is 80. One of the numbers is 100. After removing the number 100, the average becomes 78. What is value n?

 Jul 25, 2020
 #1
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he original  total of the numbers will be    80 n

then remove one number, 100 and the average becomes 78

  the new total will be   78 (n-1)        which is 100 less than the old total  80 n

    soo   78 (n-1) = 80n - 100

             78n-78 = 80n - 100

                   22 = 2n

                     n=11

 Jul 25, 2020
 #2
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sum/n = 80

80n = sum

 

(80n-100)/(n-1) = 78

80n-100 = 78n -78

-22 = -2n

n = 11

 Jul 25, 2020

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