Out of 40 consecutive integers, two are chosen at random. Find the probability that their sum is even?

• (20c2+20c2)/40c2=19/39
• 9 years agoHelpfull: Yes(7) No(0)
• even+even=even
  odd+odd=even
  40 consecutive integer will have 20 even and 20 odd numbers.
  20/40*19/39+20/40*19/39
  
• 9 years agoHelpfull: Yes(7) No(1)
• 19/39
  either to choose 2 odd no or 2 even thn sum will b even
  20c2+20c2/40c2
• 9 years agoHelpfull: Yes(4) No(0)
• Forty consecutive integers will have 20 even and 20 odd integers. The sum of 2 chosen integers will be odd, only if:
  First is even and second is odd
  First is odd and second is even
  Mathematically the probability will be given by:
  P(First is even) * P(Second is odd) + P(First is odd) + P(Second is even)
  
  = (20/40) * (20/39) + (20/40) * (20/39)
  
  = 20/39
• 9 years agoHelpfull: Yes(2) No(2)
• 20/40*20/39 + 20/40*20/39
• 9 years agoHelpfull: Yes(0) No(1)
• ans:-20c2/40c2+20c2/40c2
• 9 years agoHelpfull: Yes(0) No(0)