Find out the unit digit in the following expression ?
`91 xx 93 xx 95 xx 97 xx 98 `

Options

A. 2
B. 3
C. 0
D. 4

Answer

To find the unit digit of the expression \( 91 \times 93 \times 95 \times 97 \times 98 \), we can focus only on the unit digits of each number in the expression.

### Step-by-Step Solution:

1. **Identify the unit digits**:
- The unit digit of \( 91 \) is \( 1 \).
- The unit digit of \( 93 \) is \( 3 \).
- The unit digit of \( 95 \) is \( 5 \).
- The unit digit of \( 97 \) is \( 7 \).
- The unit digit of \( 98 \) is \( 8 \).

So, we have the unit digits: \( 1, 3, 5, 7, 8 \).

2. **Multiply the unit digits**:
- First, multiply \( 1 \) and \( 3 \):
\[ 1 \times 3 = 3 \]
- Next, multiply the result by \( 5 \):
\[ 3 \times 5 = 15 \quad \text{(unit digit is } 5\text{)} \]
- Now, multiply the result by \( 7 \):
\[ 5 \times 7 = 35 \quad \text{(unit digit is } 5\text{)} \]
- Finally, multiply the result by \( 8 \):
\[ 5 \times 8 = 40 \quad \text{(unit digit is } 0\text{)} \]

3. **Conclusion**:
The unit digit of the entire expression \( 91 \times 93 \times 95 \times 97 \times 98 \) is \( 0 \).

### Final Answer:
The unit digit of the expression is \( 0 \).