Question

A person's heartbeat is 71 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

First step: identify how many heart beats in a year.

To determine the heart beats in a year multiply the heart  beats in a minute with $(60\times 24\times 365)$ years.  

Thus, heart beats in a year comes out to be = $71 \times (60\times 24\times 365) years$

= $37317600$ heart beats in a year

Heart beats $3.1\times 10^{9}$ in a life time.

Thus, number of years he lives is calculated by the division of  heart beats in a year and heart beats in a life time.

Number of years he lives = $\frac{3.1\times 10^{9}}{37317600}$

= $8.3\times 10^{-8}\times 10^{9}$

= $8.3\times 10$

= $83.0$ years

Thus, number of years he lives is $83.0$ years