Given that a is the average (arithmetic mean) of the first eight positive multiples of six and b is the median of the first twelve positive multiples of six, what is the ratio of a to b?
Choose the correct choice.
A) 3:4	B) 10:13	C) 5:6	D) 9:13	E) 4:3
The first nine positive multiples of six are {6, 12, 18, 24,30, 36, 42, 48}   The first twelve positive multiples of six are {6, 12, 18, 24, 30,36,42, 48, 54, 60, 66, 72}   Both sets are evenly spaced, thus their median=mean:   a=(24+30)/2= 
<gadget id="calculator">(24+30)/2</gadget>
<output>27</output>
27 and b=(36+42)/2= 
<gadget id="calculator">(36+42)/2</gadget>
<output>39</output>
39 --&gt; a/b=27/39=9/13.   Answer: 9:13.
<result>D</result>
Given that a is the average (arithmetic mean) of the first eight positive multiples of six and b is the median of the first twelve positive multiples of six, what is the ratio of a to b?