Question

A person's heartbeat is 91 beats per minute. If his/her heart beats 3.1e9 times in a lifetime, how long (in whole years) does the person live? Disregard leap years.

Answer 1

During a lifetime, a heart beats 3.1 x 10^9 times and it beats 91 times in one minute.
Thus, we can use cross multiplication to determine the number of minutes in the person's lifetime as follows:
number of minutes in person's lifetime = (3.1 x 10^9) / 91 = 34.0659 x 10^6 min

One year has 365.25 days (disregarding leap). Each day has 24 hours and each hour has 60 minutes.
Therefore,
one year = 365.25 x 24 x 60 = 525960 minutes

We can now use cross multiplication to determine the number of years of a person's lifetime as follows:
number of years = (34.0659 x 10^6  x 1) / 525960 = 64.76899 years.