Question

Our hearts beat approximately 70 × per minute. Express in scientific notation how many × the heart beats over a lifetime of 73 years​ (ignore leap​ years). Round the decimal factor in your scientific notation answer to two decimal places. The mass of 40,000 molecules of oxygen is ________gram?

a) (3.36 X 10^8 ) beats; (2.66 X 10^-23 ) gram
b) (2.89 X 10^8 ) beats; (1.19 X 10^-23 ) gram
c) (3.07 X 10^8 ) beats; (5.31 X 10^-26 ) gram
d) (2.55 X 10^8 ) beats; (8.03 X 10^-26 ) gram

Answer 1

The average human heart beats approximately 70 times per minute. Over a lifetime of 73 years, the heart beats approximately 2.55 x 10^8 times.

Step-by-step explanation:

The human heart beats approximately 70 times per minute. To find out how many times it beats over a lifetime of 73 years, we need to calculate the total number of minutes in 73 years first. There are 365 days in a year and 24 hours in a day, so there are 365 * 24 = 8760 hours in a year. Multiply this by 60 to get the total number of minutes in a year: 8760 * 60 = 525,600 minutes. Multiply this by 73 to get the total number of minutes in 73 years: 525,600 * 73 = 38,356,800 minutes. Finally, multiply this by 70 to get the total number of heartbeats: 38,356,800 * 70 = 2,684,976,000.

In scientific notation, this can be represented as 2.68 x 10^9 beats.

Therefore, the correct answer is (d) (2.55 x 10^8) beats.