heart rate problem The average heart rate of a shrew is 800 beats per minute, while an elephant has a heart rate of 25 beats per minute. If 1 billion heartbeats is a natural life span for each animal, on average, how many more years do elephants live than shrews? (Assuming each year is 365 days and the answer should be rounded to the nearest whole number.)

I think the main trick is getting to _years_ given beats per _minute_.

Converting units boils down to multiplying by $1$ a bunch of times:

$$\frac{25 \text{ beats}}{\text{min}} \times \frac{60 \text{ min}}{1 \text{ hr}} \times \frac{24 \text{ hr}}{1 \text{ d}} \times \frac{365 \text{ d}}{1 \text{ yr}} = 13,140,000 \frac{\text{beats}}{\text{yr}}.$$

Everything but the first term on the left is essentially $1$: one time span over another equal time span. That, and everything except _beats_ and _year_ cancels out.

Can you take it from here?