JEE Mains Model Paper 22

Second group starts with 2 + 1 - 3 Third group starts with 2 + 4 + 1 =7
Fourth group starts with 2 + 4 + 6 + 1 = 13 so on......
Tenth group starts with (2 + 4 + 6 + ... + 18) +1 = 91
Tenth group has 20 numbers. Last but one number in it is 91 + 18 = 109.