Prealgebra -proportions

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monkeygirl

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Problem solving with proportions:

I understand how to solve proportions but am unsure how to set this one up.

About 9 out of 10 adults think it is a good idea to exersize regularly.
But of the ones who think it is a good idea, only 1 in 6 actually exersize
at least three times a week. At this rate,how many of the
300 employees in our company exercise regularly?

x=?
 
There are many ways to solve this. Keeping it organized in some way YOU understand is the most important thing. This is one way I might approach it - by making a tree.

First Level
9/10 - Good Idea
1/10 - Not a Good Idea

Second Level
9/10 - Good Idea - 1/6 Exercises
9/10 - Good Idea - 5/6 Doesn't Exercise

Apply Your Population - 300
First Level
9/10 - Good Idea - 300*(9/10) = 270
1/10 - Not a Good Idea - 300*(1/10) = 30
Check: 270 + 30 = 300 -- Good.

Second Level - 270
9/10 - Good Idea - 300*(9/10) = 270 - 1/6 Exercises - 270*(1/6) = 45
9/10 - Good Idea - 300*(9/10) = 270 - 5/6 Doesn't Exercises - 270*(5/6) = 225
Check: 45 + 225 = 270 -- Good.
 
In proportions your saposed to compare a over b right
example
a-miles a-miles
_______=_______
b-gallons b-gallons

so they have mathching units?
one of them being unknown use cross products to solve .
but I dont get how to set this one up.
 
monkeygirl said:
In proportions.... I dont get how to set this one up.
Click to expand...
You've already been provided with a complete solution. Are you saying that you are required to complete this exercise by some other method...?

Eliz.
 
No. I know how to set up, but not clear how to do this one because
there are more than four numbers 9,10,1,6,300
I dont get if I use the 9of 10 as a fraction or the 1 of 6 as a fraction
and since it is it is asking how many of the 300 exersize regularly
do I just use 1,6,300?-1over6, x over 300?
because 9out of 10 think its good so do I leave that out.

basically Im confused because its a word problem and dosent make sense .because its not asking how many of the 300 think to exersize
so how does the 9 of ten who think its a good idea fit in , the question is asking for how many of 300 employees exersise regularly

9 of 10 think to exersise

of the 9 only 1 of 6 actually exersise

300 not sure how many of these exersise regularly



so either I do them as fractions or I have to elemanate two numbers?
 
monkeygirl said:
No. I know how to set up, but not clear how to do this one because
there are more than four numbers 9,10,1,6,300
I dont get if I use the 9of 10 as a fraction or the 1 of 6 as a fraction
and since it is it is asking how many of the 300 exersize regularly
do I just use 1,6,300?-1over6, x over 300?
because 9out of 10 think its good so do I leave that out.

basically Im confused because its a word problem and dosent make sense .because its not asking how many of the 300 think to exersize
so how does the 9 of ten who think its a good idea fit in , the question is asking for how many of 300 employees exersise regularly

9 of 10 think to exersise

of the 9 only 1 of 6 actually exersise

300 not sure how many of these exersise regularly



so either I do them as fractions or I have to elemanate two numbers?
Click to expand...

How about doing the problem in two stages (which is basically what the previously demonstrated solution involved)?


Stage 1:
9 out of 10 think exercise is a good idea.
how many out of 300 think it is a good idea, then?

9/10 = x/300

10x = 2700
x = 270

So, now we know that there are 270 people who think that exercise is a good idea.

Stage 2:
1 out of 6 who think it is a good idea actually exercise. So, how many of this group of 270 actually exercise?

1/6 = y/270

Solve this proportion for y, and you will have the answer to the question "How many of the 300 people exercise regularly?"

Or, you can use this approach.
We know that 9/10 of the people say exercise is a good idea, but of these, only 1/6 actually exercise. So, 1/6 of 9/10 of the people actually exercise. 1/6 of 9/10 is

(1/6)*(9/10) = 3/20

So, 3 out of 20 responders actually exercise. And you can use this proportion:
3/20 = z/300
to determine the number of actual exercisers in the group of 300. You should get the same results as in the previously-described two-stage process.
 
"About 9 out of 10 adults think it is a good idea to exersize regularly.
But of the ones who think it is a good idea, only 1 in 6 actually exersize
at least three times a week. At this rate,how many of the
300 employees in our company exercise regularly?"

CAUTION: it is NOT STATED that the ones who do not think it is a good idea
do not exercise; like, I think it's not a good idea to smoke, but I smoke :twisted:

This should be added: the ones who think it's not good idea NEVER exercise.

Anyhoo, seems fairly easy to answer:
.9 * 300 = 270 (think it's good idea)
1/6 * 270 = 45 (exercise regularly)
 
Very good, Sir. I overlooked that important point.
 
monkeygirl said:
No. I know how to set up, but not clear how to do this one because
there are more than four numbers 9,10,1,6,300
I dont get if I use the 9of 10 as a fraction or the 1 of 6 as a fraction
and since it is it is asking how many of the 300 exersize regularly
do I just use 1,6,300?-1over6, x over 300?
because 9out of 10 think its good so do I leave that out.

basically Im confused because its a word problem and dosent make sense .because its not asking how many of the 300 think to exersize
so how does the 9 of ten who think its a good idea fit in , the question is asking for how many of 300 employees exersise regularly

9 of 10 think to exersise

of the 9 only 1 of 6 actually exersise

300 not sure how many of these exersise regularly



so either I do them as fractions or I have to elemanate two numbers?
Click to expand...

The problem is that the questioner has thrown in a few red herrings

9 out of 10 employees believe in exercise.

There are 300 employees

300 x 9/10 = 270

1 out of 6 of those who believe in exercise actually do something about it.

270 x 1/6 = 270/6 = 45.

Therefore, from the information available the answer is 45

As Denis pointed out, we have no information on those who don't think exercise is a good idea so there is not much that can be done there. And the fact that the health nuts exercise at least 3 times a week is neither here nor there.
 
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