Question

find the unit digit of 42^42

Answer 1

42⁴²=42.42.42.42.42....42(42 digits)

we have: 42¹with unit digit is 2

42² with unit digit is 4

42³with unit digit is 8

42⁴with unit digit is 6

42⁵ with unit digit is 2

so we have 4 digits of the units: 2,4,8,6

42:4=10 residual 2

so unit digit of 42⁴² is 4

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