If a = (1/3)b and c = 2a, then which of the following represents the average (arithmetic mean) of a, b, and c, in terms of a ? Options.
A) a + 4	B) 2a	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 =1/3b, which is equivalent to b = 3a. We can plug that in and simplify the average to:a + 3a + c/3   We also know that c = 2a, which we can plug directly into the average expression:   a + 3a + 2a/3   = 6a/3 = 2a, choice2a.6 /3= 
<gadget id="calculator">6 /3</gadget>
<output>2</output>
2a, choice2a.
<result>B</result>
If a = (1/3)b and c = 2a, then which of the following represents the average (arithmetic mean) of a, b, and c, in terms of a ?