Question Video: Calculating Heart Rate from Cardiac Output and Stroke Volume | Nagwa Question Video: Calculating Heart Rate from Cardiac Output and Stroke Volume | Nagwa

Question Video: Calculating Heart Rate from Cardiac Output and Stroke Volume Biology • Second Year of Secondary School

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Calculate, to the nearest whole number, the heart rate, in beats per minute (bpm), of a heart that has a cardiac output of 4,900 cm³/min and a stroke volume of 80 cm³/b.

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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.

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