A certain stock exchange designates each stock with a 1, 2 or 3 letter code, where each letter is selected from the 6 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order, constitute a different code, how many diff stocks is it possible to designate with these codes?
Options
A) 258	B) 426	C) 324	D) 542	E) 410
Pretty simple actually   Number of 1 letter symbols = 6   Number of 2 letter symbols = 6*6   Number of 3 letter symbols = 6*6*6   The answer is sum of the 3. = 258   The answer choices have their units digits unique. All 3 of the above end in 6 (6 to the power of anything ends in 6) so  6+6+6= 
<gadget id="calculator"> 6+6+6</gadget>
<output>18</output>
18 i.e. ends with 8.   So the answer is 258.
<result>A</result>
A certain stock exchange designates each stock with a 1, 2 or 3 letter code, where each letter is selected from the 6 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order, constitute a different code, how many diff stocks is it possible to designate with these codes?