Question

the unit digit in 7^105??

Answer 1

${7}^{1} = 7 \\ {7}^{2} = 9 \\ {7}^{3} = 3 \\ {7}^{4} = 1 \\ {7}^{5} = 7.... \\ {7}^{105} = 7 \times {7}^{104} \\ = 7 \times {7}^{4 \times (26)} \\ = 7 \times 1 \\ 7$
7 is your answer.