an area code composed of 2 letters

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an area code composed of 2 letters

by sanju09 » Tue May 24, 2011 1:52 am
The telephone company wants to add an area code composed of 2 letters to every phone number. In order to do so, the company chose a special sign language containing 124 different signs. If the company used 122 of the signs fully and two remained unused, how many additional area codes can be created if the company uses all 124 signs?
(A) 246
(B) 248
(C) 492
(D) 15,128
(E) 30,256

[spoiler]Source: Eric's collection on BTG


OA C[/spoiler]
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by kisor.biswal » Tue May 24, 2011 2:10 am
Answer is C 492. Explanation 124 pow 2 - 122 pow 2.