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ruhi
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The telephone company wants to add an area code composed of 08 Nov 2004, 13:31
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. 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



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Paul
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The telephone company wants to add an area code composed of 08 Nov 2004, 13:40
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Just had some trouble understanding the wording of this problem. If I'm understanding this right, it should be 124^2 - 122^2 = 492
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gayathri
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The telephone company wants to add an area code composed of 08 Nov 2004, 14:07
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Paul, can you please explain.

I thought it would be 124P2 - 122P2, but that answer would be 490 :?
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Paul
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The telephone company wants to add an area code composed of 08 Nov 2004, 14:58
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No, no. Not permutations because by doing permutations, you are assuming that you cannot use same 2 numbers whereas there is no such specifications in the question. Let's say "A" and "B" are the two extra signs for a total of 124 signs. You have AA and BB which are possible combinations which you did not account for in the permutation formula. That is why you have 2 less than my answer.
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The telephone company wants to add an area code composed of 08 Nov 2004, 20:35
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Thanks Paul, got it now! :-)



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