Video Transcript
Calculate, to the nearest whole
number, the heart rate, in beats per minute, of a heart that has a cardiac output of
4,900 cubic centimeters per minute and a stroke volume of 80 cubic centimeters per
beat.
The question asks us to calculate
the heart rate in beats per minute. We are given the cardiac output and
stroke volume. As with any math problem, we need
to begin by defining the terms we will be using to perform our calculations. Cardiac output refers to the volume
of blood the heart can pump in one minute. It is often used as a biological
marker to determine how well the heart is performing. Stroke volume refers to the amount
of blood the heart can pump in a single beat. Finally, heart rate refers to the
number of times the heart beats in one minute.
Now that we understand each key
term, let’s see how they are related to each other. You may remember the equation
cardiac output equals heart rate times stroke volume. Because the question gives us
cardiac output and stroke volume, we can insert these variables into our
equation. It now reads 4,900 cubic
centimeters per minute equals heart rate times 80 cubic centimeters per beat.
Next, we need to rearrange the
equation so that the variable we are solving for, that is, heart rate, stands
alone. We do this by dividing both sides
of the equation by the stroke volume. Any number divided by itself always
equals one, and the heart rate times one just equals the heart rate. So, our equation now states that
the heart rate is equal to 4,900 cubic centimeters per minute divided by 80 cubic
centimeters per beat. Performing this calculation to
solve for heart rate gives us 61.25 beats per minute.
But we aren’t quite done. Remember, the equation asks for us
to give heart rate as the nearest whole number, so we need to round our solution
down. So, the correct answer is 61.
