physics question regarding capacitor?

P

peacemaker

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In a heart pacemaker, a pulse is delivered to the heart 84 times per minute. The capacitor that controls this pulsing rate discharges through a resistance of 1.8 multiplied by 10^6 ohms . One pulse is delivered every time the fully charged capacitor loses 60.2% of its original charge. What is the capacitance of the capacitor?
 
Why? I might have this all wrong but hey. If it were normal time and not some off the wall time it would have been 77.77 nF. So I am thinking to get the same time constant with a shorter length of time you need a bigger capacitor, by .611. That would result in one being 127nF. Just a guess of course. A time constant being 63.21%, maybe close cant remember anymore. That would be 36.79% of charge left in cap. So if it breaks before its time at 60.2% then that is how I derived at the answer.
 
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