To find the average number of beats per second, we can calculate the total number of beats and divide it by the total time in seconds.
We will use the coordinates given:
- (4, 6): 6 beats at 4 seconds
- (6, 9): 9 beats at 6 seconds
- (10, 15): 15 beats at 10 seconds
- (12, 18): 18 beats at 12 seconds
Using the coordinates, we first calculate the total heartbeats:
- At 4 seconds: 6 beats
- At 6 seconds: 9 beats
- At 10 seconds: 15 beats
- At 12 seconds: 18 beats
Now, we find the total number of beats and the total time:
Total beats:
- 6 + 9 + 15 + 18 = 48 beats
Total time:
- The time represented by the last coordinate is 12 seconds.
Now, we can calculate the average number of beats per second:
\[ \text{Average beats per second} = \frac{\text{Total beats}}{\text{Total time}} = \frac{48 \text{ beats}}{12 \text{ seconds}} = 4 \text{ beats per second} \]
Thus, the average number of beats per second is 4 beats per second.
Since this is not one of the options you provided, there may be an error in the question or the way time and beats are interpreted. If you were looking for the average rate over intervals or as specific portions, please clarify, but based on the given data, the calculations yield 4 beats per second.