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 Post subject: Math question
PostPosted: Tue Jun 11, 2013 5:58 pm 
Chard Martyr
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Hey can some math person help me understand something...

I'm having trouble understanding the purpose of dividing by a decimal. Here's my real world dietitian example.

A patient has his entire leg amputated. A leg is 16% of a body (that's the standard percentage used). Sometimes we have to calculate adjusted body weight to determine how much someone would weigh if they were not missing a limb.

So the standard calculation for this is:
Adjusted Body Weight = Current body weight/(1-0.16)

So we divide his weight by 0.84. In sort of mathy terms this means "how many 0.84s go into 150lb" (for example)

I get HOW to do the equation, I just don't get WHY this is the calculation for this.


(There's not really any good reason that I need to understand why. I think this is why i always had trouble with math as a kid. No one would explain the why, just the how)

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 Post subject: Re: Math question
PostPosted: Tue Jun 11, 2013 6:14 pm 
Vegan Vegan Vegan Vegan Vegan
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0.84 is 84%, right?

You are trying to find out what 150lb is 84% of.

To find out what 84% of a number is, you multiply that number by 0.84.

In your example, you have a 150 pound person who is missing 16% of his body weight.

Let's get algebraic! Let X = total original body weight!

X * 0.84 = 150

Solve for X: divide both sides by 0.84:

(X * 0.84)/0.84 = 150 / 0.84

Simplify. The *0.84 and the /0.84 cancel out on the left-hand side:

X = 150/0.84.

Make sense?

(Edited for less repetition.)

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 Post subject: Re: Math question
PostPosted: Tue Jun 11, 2013 6:41 pm 
Chard Martyr
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solipsistnation wrote:
0.84 is 84%, right?

You are trying to find out what 150lb is 84% of.

To find out what 84% of a number is, you multiply that number by 0.84.

In your example, you have a 150 pound person who is missing 16% of his body weight.

Let's get algebraic! Let X = total original body weight!

X * 0.84 = 150

Solve for X: divide both sides by 0.84:

(X * 0.84)/0.84 = 150 / 0.84

Simplify. The *0.84 and the /0.84 cancel out on the left-hand side:

X = 150/0.84.

Make sense?

(Edited for less repetition.)


Yes! THANK YOU! This is a perfect explanation. I really appreciate it!

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 Post subject: Re: Math question
PostPosted: Tue Jun 11, 2013 7:16 pm 
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Yay! I can still do math! 8)

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 12:11 am 
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solipsistnation wrote:
0.84 is 84%, right?

You are trying to find out what 150lb is 84% of.

To find out what 84% of a number is, you multiply that number by 0.84.

In your example, you have a 150 pound person who is missing 16% of his body weight.

Let's get algebraic! Let X = total original body weight!

X * 0.84 = 150

Solve for X: divide both sides by 0.84:

(X * 0.84)/0.84 = 150 / 0.84

Simplify. The *0.84 and the /0.84 cancel out on the left-hand side:

X = 150/0.84.

Make sense?

(Edited for less repetition.)


ISA!!!! ISA THERE'S MATH GOING ON IN YOUR FORUMS! MAKE IT STOP!

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 6:58 am 
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No! We need more math. I was excited to answer a math question, but it was already done.


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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 3:26 pm 
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Kimba, I felt the same way!


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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 3:28 pm 
Chard Martyr
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Thanks for trying to help guys! I'm sure I'll have more math questions for you someday.

or you know, if you just want me to give you sample tube feeding calculations, you have fun with those.

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 3:58 pm 
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Is anyone else having the problem that when you try to read anything in this thread, a soulless chasm opens up on your screen, then when you stick your hand in it's wet and cold?

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 3:58 pm 
Venomous Head of Veganism
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Is anyone else having the problem that when you try to read anything in this thread, a soulless chasm opens up on your screen, then when you stick your hand in it's wet and cold?

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 4:05 pm 
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I felt more like Peter Duncan when he sticks his green-blooded wrist into the bitey tree stump in Flash Gordon.

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 4:24 pm 
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i heard windchimes, and then a bunny hopped across the screen and everything exploded into rainbow hearts.

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 4:48 pm 
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Ohhh I must be in the early phases.

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 4:55 pm 
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I recommend not sticking any other body part in there, Isa...

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 Post subject: Re: Math question
PostPosted: Wed Jun 12, 2013 5:08 pm 
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i wanted to answer a math question, too! more MATH.

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