- According to my knowledge, average heart rate is 70 beats per minute. Average human lives for 80 years, which is 80*360*24*60=41 472 000 minutes. Therefore, there are (roughly) 41 472 000*70=2 903 040 000 heartbeats.
- The volume of our planet assuming it's a sphere:
VE=34πR3. The volume of the sphere that is 4700 m below earth's surface:
VB=34π(R−4700)3. The volume of the shell 4700 m thick:
VS=VE−VB=34π[R3−(R−4700)3]. 2/3 of this volume is water:
V=32VS=98π[R3−(R−4700)3]. The mass of water:
m=ρV=98ρπ[R3−(R−4700)3]=1.60⋅1021. The order or magnitude: 1021
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