Question

Let setM = {x, 2x, 4x} for any number x. If the average (arithmetic mean) of the numbers in set M is 14, what is the value of x ?
a.6
b.7
c.10
d.12
e.14

Answer 1

How do you calculate and average?

Answer 2

average a,b,c,d = (a+b+c+d)/4

in this case we have x, 2x, 4x whose average is 14
this implies that (x+2x+4x)/3 =14

or (x+2x+4x) = (14)(3)
or 7x = (14)(3)
or x= (14)(3)/7
or x= (2)(3)
or x=6