+0  
 
0
339
2
avatar

How many 2-letter "words" consist of two different letters arranged in alphabetical order? (Any two letters together is considered a "word.")

Guest Mar 14, 2015

Best Answer 

 #2
avatar+81045 
+10

Notice that "a" could come first and be matched with 25 letters  {the rest of them} for a total of 25 words

'b' could come first and be matched with 24 letters for a total of 24 words

"c" could come first and be matched with 23 lettters for a total of 23 words

etc........

So....this appears to just be the sum of the first 25 integers = [26 * 25] / 2  = 325

Hey....Melody and I agree on something!!!

 

  

CPhill  Mar 15, 2015
Sort: 

2+0 Answers

 #1
avatar+91469 
+10

any earlier letter then z      

any earlier letter then y

----

ab

25*1+24*1+23*1 +    .....  +2*1+1

25+24+23+22+     +1

1+2+3+.......+25

this is an AP

a=1  d=1   n=25

Sn=(n/2) (a+L)

S_25 = 12.5(1+25)=12.5*26 = 325

I think that there are 325 possibilities.     

Melody  Mar 15, 2015
 #2
avatar+81045 
+10
Best Answer

Notice that "a" could come first and be matched with 25 letters  {the rest of them} for a total of 25 words

'b' could come first and be matched with 24 letters for a total of 24 words

"c" could come first and be matched with 23 lettters for a total of 23 words

etc........

So....this appears to just be the sum of the first 25 integers = [26 * 25] / 2  = 325

Hey....Melody and I agree on something!!!

 

  

CPhill  Mar 15, 2015

13 Online Users

avatar
avatar
avatar
We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.  See details