What is the number of ways in which three numbers in A.P. can be selected from the given set {1, 2, 3, 4, 5, ……….. , 121}?

(Q). What is the number of ways in which three numbers in A.P. can be selected from the given set {1, 2, 3, 4, 5, ……….. , 121}?
Solution:-

The given set { 1, 2, 3, 4, 5, ………..121} has  odd &  even integers.
now let three numbers from this set which are in A.P. be a, b, c