Given four different numbers, the average of first three numbers is four times the fourth number and the average of all the four numbers is 52. What is the average of the first three numbers?
Let the four numbers are a, b, c, d
a+b+c+d=$$4\times52=208\ $$
$$\frac{a+b+c}{3}=4d$$
a+b+c=12d
add number d in both side
a+b+c+d=13d
208=13d
d=16
So, required average =Â $$4\times16=64\ $$.
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