Chemistry set up help?

Question

Ok i need some help. here's the problem.

An average human heart beats appr. 70 beats a minute. How many beats are there after 80 yrs?

I set it up like this:

70bpm (1 hr/ 60min) (1 day/ 24 hr) (1 yr/ 365days)= bpm in a year

That gives me a really small number and I know I need to multiply but I thought I had to put what I had on bottom. Like start with minutes, put minutes on the bottom.

Any help's great.

Thanks

Answer 1

to add to your answer and to Sara's answer (which is great by the way),

this conversion is a typical "unit factor" or "factor label" or "dimensional analysis" problem...

usually, the best way to start is with the single quantity that you are given... 80 years in this case....then multiply that by your conversion factors to cancel out units...

80 years x (365 days / year) x (24 hrs / day) x (60 min / hr) x (70 beats / min) = 2.94 x 10^9 beats...

of course if you consider leap year, then there are 365.25 days in a year and....

80 years x (365.25 days / year) x (24 hrs / day) x (60 min / hr) x (70 beats / min) = 2.95 x 10^9 beats...

Answer 2

Ok.  So it looks like you probably forgot that 70bpm in itself is a fraction just like everything else.

Set it up as follows:

70 beats/min * 60 mins/hour * 24 hours/day * 365 days/year * 80 years

Your answer then would be 2,943,360,000 beats in 80 years