Given: The series is 3, 7, 13, 21, 31, ?, 57 Calculation: The series is square of Natural numbers starting from 1 with addition of next natural number in it. 12+2=3 22+3=7 32+4=13 42+5=21 52+6=31 62+7=43 72+8=57 ∴ For missing term which is the 6th term it will be 43.