Final answer:
To calculate the dog's heart rate, measure the distance between R waves on the ECG and use the formula (25 / d) * 60 bpm. This gives the heart rate in beats per minute.
Step-by-step explanation:
To determine the dog's heart rate when the ECG paper is running at 25 mm/sec, you would measure the distance between two R waves on the ECG, which correspond to the heartbeats. Suppose this distance is 'd' millimeters. The time between two heartbeats (R-R interval) would then be 'd' mm divided by the paper speed (25 mm/sec), giving us the time per beat in seconds. The heart rate in beats per minute (bpm) is found by taking the inverse of the time per beat in seconds and multiplying by 60 sec/min. Mathematically, the heart rate is calculated as (25 / d) * 60 bpm.