The last digit of the number obtained by multiplying the numbers 81 × 82 × 83 × 84 × 86 × 87 × 88 × 89 will be

Answer: Option B

The last digit of multiplication depends on the unit digit of (81 × 82 × 83 × 84 × 86 × 87 × 88 × 89) which is given by the remainder obtained on dividing it by 10.

$$\begin{array}{rl}& \frac{\left(81\times 82\times 83\times 84\times 86\times 87\times 88\times 89\right)}{10}\\ & \text{We}\text{take}\text{individual}\text{remainder}\text{of}\text{each}\text{digit,}\\ & \frac{\left(1\times 2\times 3\times 4\times 6\times 7\times 8\times 9\right)}{10}\\ & \text{Numbers}\text{multiplied},\\ & \frac{\left(24\times 42\times 72\right)}{10}\\ & \text{Individual}\text{Remainder}\text{has}\text{been}\text{taken},\\ & \frac{\left(4\times 2\times 2\right)}{10}\\ & Or,\frac{\left(16\right)}{10}\\ & Or,6\\ & \text{Remainder}=6\\ & \text{So,}\text{the}\text{last}\text{digit}\text{will}\text{be}6\end{array}$$