Math Is Fun Forum

winkylocc

Member

Registered: 2011-07-06

Posts: 6

Data problem

I really struggle with any type of word problem. I wish there was a resource that focused on these specifically. My latest struggle is as follows:

According to data from the Center for Science in the Public Interest, the healthy weight range of a person depends on the person's height. For example,

Height          Healthy Weight Range (lb)

5 ft 8 in.        143 + or - 21
6 ft 0 in.        163 + or - 26

I then have to express each of these ranges as an absolute-value inequality in which x is the weight of the person. Help...

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Data problem

hi winkylocc

I think you want

for the first one.

Just take 21 off 143 for the lower value, and add 21 on for the upper value.

Can you do the other one yourself, now?

Bob (980)

Last edited by Bob (2011-07-13 08:15:23)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

winkylocc

Member

Registered: 2011-07-06

Posts: 6

Re: Data problem

Yes I can. The absolute-value aspect threw me off.

winkylocc

Member

Registered: 2011-07-06

Posts: 6

Re: Data problem

Was actually simple. 137=< x =<189
I included the or equal to since both 137 and 189 are options.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: Data problem

hi winkylocc

Yes, that's it exactly.

I wondered about adding the = to the inequalities.  I'm sure you're right.  But if my teacher told me off for leaving the = out, I would argue that, since it is not possible to have an exact value in practice, the two are equivalent. 

Bob (982)

Last edited by Bob (2011-07-14 01:16:27)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

TMorgan

Member

Registered: 2011-04-13

Posts: 25

Re: Data problem

Hi Bob and Winky,
  I saw this post but wasn't able to reply because my computer was down. Sorry for this being so late. I think to just compute the upper and lower limits does not show you understand the concept of the absolute value. The absolute value can be used because a person's weight could be above or below the target value and still be within the limits.
  My answer for 5'8" would be (and I still haven't learned the math shorthand):

ABS (x - 143) < 21

  Inside the parenthesis could also be 143 - x.

  See Bob's last post about whether to use (less than) or (less than or equal to). You can also change the 21 to 22.

Hope this helps and isn't too late.

Tom Morgan

anonimnystefy

Real Member

From: Harlan's World

Registered: 2011-05-23

Posts: 16,049

Re: Data problem

hi bob bundy

since it is not possible to have an exact value in practice, the two are equivalent.

actually the probability is an infinitesimal.but if there is a possibility that any number is chosen at random from our interval then there is a possibility for an exact value to occure.

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“Here lies the reader who will never open this book. He is forever dead.
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment
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