Explanation 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