If a = (1/2)b and c = 8a, then which of the following represents the average (arithmetic mean) of a, b, and c, in terms of a ? Pick one:
A) a + 4 B) (11/3)a C) 4a D) (4 1/7)a E) (7 1/4)a
Official Answer: B   The average of the three variables isa + b + c/3. However, we need to solve in terms of a, which means we must convert b and c into something in terms of a.   Were told that a =1/2b, which is equivalent to b = 2a. We can plug that in and simplify the average to:a + 2a + c/3   We also know that c = 8a, which we can plug directly into the average expression:   a + 2a + 8a/3   = 11a/3=(11/3)a , choice(11/3)a.
<result>B</result>
If a = (1/2)b and c = 8a, then which of the following represents the average (arithmetic mean) of a, b, and c, in terms of a ?