RRB RPF RPSF SI and CONS Model Papers 6 with solutions

(1) The unit’s place digit of 129${}^{121}$+ 7867 = Unit’s place digit of 129${}^{121}$ + Unit’s place digit of 78${}^{67}$ = Unit’s place digit of 9${}^{121}$ + Unit’s place digit of 8${}^{67}$
= Unit’s place digit of 9${}^1$ + Unit’s place digit of 8${}^3$ (since the order of cycles of 9 and 8 are 2 and 4, respectively)
∴Unit’s place digit of (9 + 2) = 1