Quick
Answer:
It takes about 15
minutes for a heart to beat 1000 times.
On January
10, 2000, your
heart would have beat about 1 million times.
27 years later your
heart would reach about 1 billion beats. 

Complete
Solution:
By estimating, you can often find a reasonable
answer more quickly. Round your number of heartbeats to
a number that is easy to use for calculation. For example,
if your heart beats 72 times per minute, 70 beats per
minute would give a reasonable estimate.
Beats
per Hour 
Beats
per Day 
Estimated
Beats per Day 
70
× 60
= 4,200 
4,200
× 24
= 100,800 
4,000
× 25 = 100,000 
Next find how many days it takes for 1 million heartbeats:
1,000,000 ÷ 100,000 = 10.
Thus, 1,000,000 beats take 10 days.
If you begin counting on January 1, the millionth beat
will be on January 10. For 1 billion heartbeats, the number
of days is 1,000,000,000 ÷ 100,000 = 10,000. Since
there are 365 days in a year, and 10,000 ÷ 365
is approximately 27.4, it will take about 27.4 years.
The billionth beat will be in May 2027. 
