# Chapter 1 - Review - Exercises - Page 134: 24

My heart will beat $3.786912 \times 10^{9}$ times during my lifetime.

#### Work Step by Step

There are 60 minutes in one hour so the heart beats $80(60)=4800$ times in on hour. There are 24 hours in a day so the heart beats $4800(24) = 115200$ times in a day. There are $365\frac{1}{4}$ days in a year so the heart beats $115,200(365.25) = 42,076,800$ in a year. Thus, if I live for 90 years, my heart will beat a total of $42,076,800(90) = 3,786,912,000$ times. Writing this in scientific notation gives: $3,786,912,000 = 3.786912 \times 10^{9}$

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