Question
There are 15 numbers such that average of first 12
numbers is 50 while the average of last five numbers is 60. Find the 12th number, if the ratio between 11th and 12th number is 13:7, respectively.Solution
Sum of first 12 numbers = (12 x 50) = 600 Sum of last 5 numbers = (60 x 5) = 300 Sum of 11th and 12th number = (600 - 300) = 300 So, 12th number = 300 x (7/20) = 105
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