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RRB RPF RPSF SI and CONS Model Papers 6 with solutions

Question : 120 of 120

Marks: +1, -0

129^{121}+78^{67}

Solution:

(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

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