Calculating Heart Rate: Equation and Formula

Given that the heart rate r (in beats per minute) is 4 times the number of heartbeats h counted in 15 seconds, we can write the equation:

```

r = 4 * (h / (15/60))

```

Simplifying the equation:

```

r = 4 * (h / 0.25)

```

```

r = 16 * h

```

Therefore, the equation to find the heart rate r in beats per minute is r = 16h, where h represents the number of heartbeats counted in 15 seconds.