SOLUTION: the average of first three numbers is double from fourth no. if the average of all four number is 28 find out the fourth number

Question 1023101: the average of first three numbers is double from fourth no. if the average of all four number is 28 find out the fourth number
Answer by god2012(113) (Show Source): You can put this solution on YOUR website!
Let the numbers be a,b,c and d.
Average of first 3 numbers is double the 4th
(a+b+c)/3 = 2d => (a+b+c) = 6d -----------eq.1
Avg. of all 4 numbers is
(a+b+c+d)/4 = 28 => /(a+b+c+d) = 28*4 = 112 ----eq.2
Put eq.1 in eq.2
6d + d = 112
7d = 112
d = 112/7
d = 16
So, the 4th number is 16
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