A cell's division time is 1 minute, in 20 minutes, a culture tube (culture medium) is `1//8^(th)` filled with cells. When the tube will be fully filled?

Options

A. 21 minutes
B. 23 minutes
C. 60 minutes
D. 160 minutes

Explanation

To solve the problem, we need to understand how cell division works and how it affects the filling of the culture tube over time.

### Step-by-Step Solution:

1. **Understand the Division Time**: The cell divides every 1 minute. This means that after each minute, the number of cells doubles.

2. **Initial Condition**: After 20 minutes, the culture tube is filled to \( \frac{1}{8} \) of its capacity.

3. **Calculate Cell Growth**:
- At 20 minutes, the tube is \( \frac{1}{8} \) filled.
- In the next minute (21 minutes), the number of cells will double, so the tube will be \( \frac{1}{8} \times 2 = \frac{1}{4} \) filled.
- At 22 minutes, it will double again: \( \frac{1}{4} \times 2 = \frac{1}{2} \) filled.
- At 23 minutes, it will double once more: \( \frac{1}{2} \times 2 = 1 \) (fully filled).

4. **Conclusion**: Therefore, the culture tube will be fully filled after 23 minutes.

### Final Answer:
The culture tube will be fully filled in **23 minutes**.

---