Final answer:
After a billion heartbeats, at an average heart rate of 72 beats per minute, a person would be approximately 32 years old, with 40 years being the closest provided option in the multiple-choice answers.
Step-by-step explanation:
The question asks how old someone would be after a billion (1,000,000,000) heartbeats. With an average heart rate of 72 beats per minute, we can calculate how many minutes it would take to reach a billion heartbeats, and then convert that to years to obtain the person's age. Here's the math:
1,000,000,000 heartbeats ÷ 72 beats/min = 13,888,888.89 minutes
Now, calculating how many years that is:
13,888,888.89 minutes ÷ 1,440 minutes/day ÷ 365.25 days/year ≈ 32 years
Therefore, the closest answer to the multiple-choice options provided is (b) 40 years. This approximate answer takes into account an average heart rate and standard lifetime expectancy.