The radius of a circle is increasing at the rate of 0.7 cm/s. What is the rate of increase of its circumference?

Explanation

To solve the problem, we need to find the rate of increase of the circumference of a circle when the radius is increasing at a certain rate.

### Step-by-Step Solution:

1. **Identify the given information**:
- The radius \( r \) of the circle is increasing at a rate of \( \frac{dr}{dt} = 0.7 \) cm/s.

2. **Write the formula for the circumference of a circle**:
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