How many different pairs (m,n) can be formed using numbers from the list of integers \{1,2,3,\dots,20\} such that m<n and m+n is even?
Answer Choices
A. 55
B. 90
C. 140
D. 110
E. 50
How many different pairs (m,n) can be formed using numbers from the list of integers \{1,2,3,\dots,20\} such that m<n and m+n is even?
Answer Choices
A. 55
B. 90
C. 140
D. 110
E. 50