UPSC NDA Math Model Paper 3

For the first case
The terms are
17,21,25,29,33,37,41,45,49,53,57,61 ...etc.
For the second case
The terms are
16,21,26,31,36,41,46,51,56,61,66,71 .... etc
The sequence with common term becomes 21,41,61...
a1=21, d = 41 - 21 =20, n = 20
Hence Sum=n∕2[2a1+(n−1)×d]
=20∕2[2(11)+(10−1)×20]=1110
Hence, option (3) is correct.