Question

during exercise the recommended maximum heart rate in beats per minute is modeled by the formula m = 176 - 0.8A, where M is the maximum heart rate and A is the persons age. aproximately, at what age would you have recommended heart rate in beats per minute of 135?

A. 25 years
B. 39 years
C. 51 years
D. 53 years

Answer 1

@texaschic101 @SmoothMath @EclipsedStar @freckles @jagr2713 @KyanTheDoodle @sasogeek @dan815

Answer 2

Ok now we know that m is the rate right?

Answer 3

@HotPinkGirl

Answer 4

right

Answer 5

Ok so in the question it says m is 135. Now we know that the rate is 135

Answer 6

We plug in the number

Answer 7

\[135= 176 - 0.8A\]

Answer 8

This is the equation we want to solve for A which is the age of the person.

Answer 9

Are you understanding until now? :)

Answer 10

no

Answer 11

What is the thing that is confusing you

Answer 12

how do we get the answer?

Answer 13

Oh but I still did not finish yet. Did you understand that m is the rate so we have to replace it with 135?

Answer 14

yes

Answer 15

Ok awsome let's move on

Answer 16

\[135= 176 - 0.8A\]
\[135 - 176 = 176 - 0.8A - 176\]

Answer 17

Ok now we want to only get A, so we have to take 176 to the other side, which becomes negative. ALWAYS remember that when you do something to one side you have to do it to the other side as well. For example:

x +2 = -4
x+ 2 -2= -4 -2
x= -6

Answer 18

Do you understand?

Answer 19

@HotPinkGirl

Answer 20

yes

Answer 21

Awsome! :D

Answer 22

ok after doing \[135 - 176 = - 0.8A\]

Now we do the left side which we get

\[-41= -0.8A\]

Answer 23

ok do you understand this as well?

Answer 24

yes

Answer 25

\[-41= -0.8A\]

Answer 26

What should we do now? Remember when we do something to oneside, we have to do it to the other side as well.

Answer 27

@HotPinkGirl are you with me?

Answer 28

yes

Answer 29

so what should we do know?

Answer 30

now we do the other side

Answer 31

ok how?

Answer 32

\[-41= -0.8A\]

We are solving for A. That means A has to stay and does not change. Thus, what number changes?

Answer 33

-41

Answer 34

-41 changes, but for the right side we have -0.8A. What number should be removed?

Answer 35

0.8

Answer 36

-0.8 well done. Do not forget the negative sign.
Now we have to do it like this.

\[\frac{ -41 }{ -0.8 }= \frac{ -0.8A }{ -0.8 }\]

Answer 37

The rule is when we do something to one side we have to do it to the other side as well.

Answer 38

Now A= ?

Answer 39

51 years?

Answer 40

You are right. Perfext. :D

@HotPinkGirl if you liked my answer please give me a medal. I would appreciate if you write me a fan testimonial as well. Thank you!

Answer 41

ok, thanks

Answer 42

Your welcome. :)