Math Is Fun Forum

paxnatus

Member

Registered: 2009-09-11

Posts: 5

Ratio - Proportion

Hi...I can't figure this out.  Can anyone send me to a site that explains this clearly or provide a solution with an explanation would even be better.

Boyd leaves home to visit Carlene, the race-car     
driver. At the same time, Carlene leaves home to visit Boyd.     
They each proceed at a steady rate along the same road. After     
passing each other, Boyd takes 25 times as long to complete     
the trip as Carlene. Find the ratio of their speeds.

Even though it's a ratio don't I still need one more piece of info?  I have an idea of what to do but I can get it to work out. Thanks!

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Ratio - Proportion

Can anyone send me to a site that explains this clearly or provide a solution with an explanation would even be better.

Hi paxnatus;

This is a problem for "problem of the week". I thought it was a contest? If I give you the answer thats not right. If I am in error about this please show me. I will gladly attempt to do the problem.

Go here this will help a little:

http://74.125.95.132/search?q=cache%3A- … l=en&gl=us

Last edited by bobbym (2009-09-11 06:36:07)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

paxnatus

Member

Registered: 2009-09-11

Posts: 5

Re: Ratio - Proportion

Ok...so that's where my teacher found this question.  I looked at the solution but I still don't get it.  25:1 is the ratio of their times.  does that mean that bh/c and ch/b are equal to their times?  How do you get that...those ratios?  How did they simplify the equation in the solution to 1/5?  I am so confused!  Algebra is the devil!!

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Ratio - Proportion

Hi paxnatus;

I might be able to help if you showed what was being simplified.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

paxnatus

Member

Registered: 2009-09-11

Posts: 5

Re: Ratio - Proportion

Ok...here's the solution they give...

First they say to create 2 ratios for the times (that's what my teacher said to do too) and then they give these in the solution:

25/1 and ch/b:bh/c  (how do you get the second one????)

Then they set the ratios equal to each and say to find the ratio b/c....

25/1 = (ch/b)/(bh/c)

25(bh/c)= ch/b

b/c = 1/5

That's all they have beside the info in the question.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Ratio - Proportion

Hi paxnatus;

Then they set the ratios equal to each and say to find the ratio b/c....

25/1 = (ch/b)/(bh/c)

25(bh/c)= ch/b

b/c = 1/5

That is all okay.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

paxnatus

Member

Registered: 2009-09-11

Posts: 5

Re: Ratio - Proportion

but i asked where did the second ratio came from...i know i'm being dense but i just don't see it...sorry...if you can't spend any more time on this don't worry...i'll ask her on monday.  i guess there are substitutions happening but i can't see them.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Ratio - Proportion

Hi;

Your not being dense, I am the one that is dense, I am not getting it either. When she tells you tell me.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

paxnatus

Member

Registered: 2009-09-11

Posts: 5

Re: Ratio - Proportion

how do you make this step i guess is my question?  it looks like someone is doingsteps in their head here but not putting them in the solution and that's really frustrating because i can't do that so i don't understand how they did it.  oh well...like my dad says...go on to the next question. : )

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Ratio - Proportion

Hi paxnatus;

This is an easier solution:

If c speed is 2 b then they meet 1 / 3 of the way from b"s starting point. Now b has twice the distance to go and half the speed of c so it takes him 4 times longer:

If c speed is 3 b then they meet 1 / 4 of the way from b"s starting point. Now b has 3 times the distance to go and 1/ 3 the speed of c so it takes him 9 times longer:

If c speed is 4 b then they meet 1 / 5 of the way from b"s starting point. Now b has 4 times the distance to go and 1/ 4 the speed of c so it takes him 16 times longer:

If c speed is 5 b then they meet 1 / 6 of the way from b"s starting point. Now b has 5 times the distance to go and 1/ 5 the speed of c so it takes him 25 times longer:

You see the ratio of speeds is 5 to 1 for 25 times as long.

Last edited by bobbym (2009-09-11 08:01:28)

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.