Two distinct no's are taken from 1,2,3,4......28 Find the probability that their sum is less than 13

• first we will compute the total sample space
  sample space: all possible combination of 2 numbers
  28c2=378
  now favourable outcomes:
  starting with 1 we have (1,2),(1,3)......(1,11)=10outcomes
  starting with 2 we have (2,3),(2,4)......(2,10)=8outcomes
  here(2,1) is not considered since (2,1)and(1,2) are same numbers
  
  similarly,
  starting with 3 we have 6 outcomes
  starting with 4 we have 4 outcomes
  starting with 5 we have 2 outcomes
  so total no of favourable outcomes=(10+8+6+4+2)=30
  so required probability=30/378=5/63
• 9 years agoHelpfull: Yes(28) No(1)
• sruthi...can u plz tell me what all rounds were conducted by cts...
• 9 years agoHelpfull: Yes(7) No(2)
• sruthi .. can you please tell me when did you appear for d congnizant xam.. and who conducted it ..cocubes or else AMCAT ?
• 9 years agoHelpfull: Yes(6) No(0)
• we can also get a outcome from 6 i.i (6,6) makes 12 which is less than 13 @ gaurav kumar
  
• 9 years agoHelpfull: Yes(3) No(0)
• 
  ans : 2/21
  
  starting with 1 ,the possible pairs are (1,1),(1,2),(1,3)......(1,11)=11outcomes
  starting with 2,the possible pairs (2,2)(2,3),(2,4)......(2,10)= 9 outcomes
  here(2,1) is not considered since (2,1)and(1,2) are same numbers
  
  similarly,
  starting with 3 we have 7 outcomes
  starting with 4 we have 5 outcomes
  starting with 5 we have 3 outcomes
  starting with 6 we have 1 outcome (that is (6,6)
• 9 years agoHelpfull: Yes(1) No(5)
• @neha, i have just attended cts mock test through amcat which was conducted in my university by cts.
• 9 years agoHelpfull: Yes(0) No(1)
• sruthi if you dont mine can you plz tell me whether any qusetions related to c,c++ or something else like technical were asked in the test .
• 9 years agoHelpfull: Yes(0) No(0)
• @khoushik . yeah.. related to mobility, cloud computing, computernetworks, datastructures,operating systems, and dbms. not c, c++, java.
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