# Find Expression for Cost y

• Sep 28th 2013, 10:08 AM
nycmath
Find Expression for Cost y
A 50 cm length of ribbon costs x dollars. Find an expression for the cost of y meters of ribbon. Give your answer to its simplest form.

My solution:

Let y = the total cost for a certain amount of x ribbons

Let x = the cost per ribbon

I write a linear equation to express a relation between x, y and 50.

I say the equation is y = 50x.

Is this correct? If not, why not?
• Sep 28th 2013, 10:17 AM
topsquark
Re: Find Expression for Cost y
Quote:

Originally Posted by nycmath
A 50 cm length of ribbon costs x dollars. Find an expression for the cost of y meters of ribbon. Give your answer to its simplest form.

My solution:

Let y = the total cost for a certain amount of x ribbons

Let x = the cost per ribbon

I write a linear equation to express a relation between x, y and 50.

I say the equation is y = 50x.

Is this correct? If not, why not?

It looks good to me. However the 50 is in cm, while y is to be measured in m.

-Dan
• Sep 28th 2013, 10:57 AM
votan
Re: Find Expression for Cost y
Quote:

Originally Posted by nycmath
A 50 cm length of ribbon costs x dollars. Find an expression for the cost of y meters of ribbon. Give your answer to its simplest form.

My solution:

Let y = the total cost for a certain amount of x ribbons

Let x = the cost per ribbon

I write a linear equation to express a relation between x, y and 50.

I say the equation is y = 50x.

Is this correct? If not, why not?

The cost x dollars is for 50 cm. You need first to convert those to m. Yhen use that number to calculate the cost of y meters.
• Sep 28th 2013, 12:46 PM
HallsofIvy
Re: Find Expression for Cost y
You say "y = the total cost for a certain amount of x ribbons" and "Let x = the cost per ribbon"

So is "x" a number of ribbons or the cost per ribbon?

In your "y= 50x" what does "x" represent?
• Sep 28th 2013, 01:32 PM
votan
Re: Find Expression for Cost y
Quote:

Originally Posted by HallsofIvy
You say "y = the total cost for a certain amount of x ribbons" and "Let x = the cost per ribbon"

So is "x" a number of ribbons or the cost per ribbon?

In your "y= 50x" what does "x" represent?

OP question is x is the cost of 50 cm, or 0.5 m. from which you get the cost of one meter is x/0.5 = 2x. The cost of y meters would be..

y is the cost of a number of meters of ribbon, not the number of ribbons
• Sep 28th 2013, 03:13 PM
HallsofIvy
Re: Find Expression for Cost y
Quote:

Originally Posted by votan
OP question is x is the cost of 50 cm, or 0.5 m. from which you get the cost of one meter is x/0.5 = 2x. The cost of y meters would be..

y is the cost of a number of meters of ribbon, not the number of ribbons

You got that from
"Let y = the total cost for a certain amount of x ribbons

Let x = the cost per ribbon"

I'm impressed!
• Sep 29th 2013, 02:10 PM
nycmath
Re: Find Expression for Cost y
Quote:

Originally Posted by HallsofIvy
You got that from
"Let y = the total cost for a certain amount of x ribbons

Let x = the cost per ribbon"

I'm impressed!

Are you impressed with Votan?
• Sep 29th 2013, 05:05 PM
HallsofIvy
Re: Find Expression for Cost y
Isn't everyone? My point was that your initial statement of the problem was very confused, using "x" for two different things. But Votan was able to make sense of it!