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MATH PRACTICE: The Circulatory System

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Measuring some things can be difficult.  For example, think of the heartbeat.  When do you begin to count?  When do you stop? 

There are measurements that only make sense when they are compared to something else. These measurements are called rates.

Look at this sentence:

          A male’s heart beats about 70 times per minute.

Heartbeats make sense only when they are related to a time frame, like a minute. 

For example, for a thirty-year-old man, a heartbeat rate of 70 is normal.  A heartbeat of 140 when exercising is fine.  A heartbeat of 250 is dangerous.  In all of these measurements, it is understood that the number of heart beats happened in a minute.  (70 beats a minute; 140 beats a minute; 250 beats a minute)

Activity 1

Find a clock or watch with a second hand.  Locate your heartbeat either on the inside of your wrist, at the base of the thumb, or on the side of your neck about an inch below the end of the jaw. 

Count the beats for 30 seconds.  There are 60 seconds in a minute.What is your heartbeat rate per minute?

There are 60 minutes in an hour.  What would your heartbeat be per hour? 

There are 24 hours in a day.  What would your heartbeat be per day?  It’s easy to see why a minute is the time frame used for this rate.

HELP:  I counted 40 beats in 30 seconds. To get my heart rate for 60 seconds, or one minute,  I would double that amount (40 X 2=80).

There are 60 minutes in an hour. To get my heart rate for 1 hour, I would multiply 80 beats (1 minute) by 60 (80 X 60 = 480).

There are 24 hours (60 minutes X 24) in a day. To get my heart rate for a day, I would....

Problem 2

Explain to about 6 people that you know well that you want to learn how to measure heart rates.  Ask if they or you can check their heartbeat.  Take these measurements for 15 seconds.  Try to include a child, an athlete, and an old person in your selection of people.  How do their heart beat rates per minute compare?

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What other things can you think of that are measured in comparison to something else? (Hint: miles per gallon).