Quantitative Aptitude

The unit digits of powers of 7 follow a cycle of period 4: $7^1 = 7$ $7^2 = 9$ $7^3 = 3$ $7^4 = 1$ Dividing the exponent 105 by 4: $105 = 4 \times 26 + 1$ The remainder is 1, so the unit digit is identical to $7^1 = 7$.