Cost word problem 2 and 3 System of Linear Equation with two variables

[chr251287]

How do I set up these word problems?
The postal service charges 33 cents for letters that weigh 1 ounce or less and 22 cents more for letters that weigh between 1 and 2 ounces. Jeffery, testing his father's math skills, gave his father $37.40 and asked him to purchase 80 stamps for his stamp collection, some 33-cent stamps and some 55-cent stamps. How many of each type of stamp did he buy?
x+y=$37.40
0.33x+0.55y=80($37.40)

A grocer wants to mix two kinds of nuts. One kind sells for 70 cents per pound, and the other sells for $1.30 per pound. He wants to mix a total of 20 pounds and sell it for 82 cents per pound. How many pounds of each kind should he use in the new mix?
x+y=20
0.70x+0.82=20(0.82)

Is that the correct method? I am not 100% sure.

 

[mmm4444bot]

[Jeffery] gave his father $37.40 and asked him to purchase 80 stamps for his stamp collection, some 33-cent stamps and some 55-cent stamps. How many of each type of stamp did he buy?

x + y = $37.40

0.33x + 0.55y = 80($37.40)

:idea: Do not include the dollar signs in your equations.

Thank you for including some work. Firstly, I think that you should write down your definitions for symbols x and y. That way, other people will know what you chose the symbol x to represent and what you chose the symbol y to represent.

I will assume the following, but defining symbols that you pick should be the first step in most word problems.

Let x = the number of 33-cent stamps bought

Let y = the number of 55-cent stamps bought



Okay -- now that everybody knows the meaning of x and y, let's take a look at your first equation:

x + y = 37.40

This equation models the following statement.

The total number of stamps bought is 37.4



This is your second equation:

0.33x + 0.55y = 80(37.40)

This equation models the following statement.

The total value of the stamps bought is 80 times $37.40



Is this enough information for you to be able to correct your equations? :cool:

If so, please post your corrected equations, and tell us your thoughts on how you might begin to solve for x and y. Cheers

 

[mmm4444bot]

[WRITING down what symbols stand for is also important] so that YOU will not forget what each symbol means

Exactly.

If a person keeps track that x means some number of stamps and y also means some number of stamps, then they would be unlikely to write x+y=37.4

:idea: Learning math is a process of making mistakes, recognizing what's wrong, correcting, and moving on. It's better to get these types of basic mistakes out of your toolbox as soon as possible. :idea:

 

[chr251287]

Thank you very much!