Four numbers are chosen from {1,2,3.....20} n(S)=20C4 Statement-1: Common difference is 1; total number of ways = 17 common difference is 2; total number of ways = 14 common difference is 3; total number of ways = 11 common difference is 4; total number of ways = 8 common difference is 5; total number of ways = 5 common difference is 6; total number of ways = 2 Prob. =
17+14+11+8+5+2
20C4
=
1
85
Statement -2 is false, because common difference can be 6 also.