A person's heartbeat is 61 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.

In this question, you are asked the time but given the speed (61beat/min) and the number of beats (3.1 x 10^9). Then the equation would be:

Time = number of beats / speed

Time = 3.1 x 10^9 beats / (61 beats/min) = 5.081 x 10^7 minutes.

Then convert it to years, disregard of leap years it would be : 5.081 x 10^7 minutes / (60 minutes/hour) / (24 hour/day) / (365 day/year) = 96.69 years