The efficiency of a cell when connected to a resistance `R` is `60 %`. What will be its efficiency if the external resistance is increased by six times?

Explanation

To solve the problem, we need to calculate the efficiency of a cell when the external resistance is increased by six times, given that the initial efficiency is 60%.

### Step-by-Step Solution:

1. **Understanding Efficiency**:
The efficiency (η) of a cell is defined as the ratio of output power to input power. Mathematically, it can be expressed as:
\[
\eta = \frac{P_{\text{out}}}{P_{\text{in}}}
...