1. ## Number of Items

Let me try a different approach to word problems in terms of creating the right equation. I will convert (in parts) from words to algebraic language and indicate where I get stuck.

A certain manufacturer produces items for which the production costs consist of annual fixed costs totalling 130,000 dollars and variable costs averaging 8 dollars per item.

I understand the above to mean 130, 000 + 8x. Obviously, x must equal the number of items.

If the manufacturer's selling price per item is 15 dollars, how many items must the manufacturer produce and sell to earn an annual profit of 150,000 dollars?

Here is where I got stuck. It cannot be 15x + 150,000.

Help.

2. ## Re: Number of Items

Profit is revenue minus costs. Assuming all items produced are sold, this gives us:

$\displaystyle P(x)=R(x)-C(x)=(15x)-(8x+130000)=7x-130000$

Now, to determine the number of items produced and sold to generate the given profit, we would write:

$\displaystyle P(x)=150000$

$\displaystyle 7x-130000=150000$

Solving this for $\displaystyle x$ will answer the question.

3. ## Re: Number of Items

Originally Posted by MarkFL
Profit is revenue minus costs. Assuming all items produced are sold, this gives us:

$\displaystyle P(x)=R(x)-C(x)=(15x)-(8x+130000)=7x-130000$

Now, to determine the number of items produced and sold to generate the given profit, we would write:

$\displaystyle P(x)=150000$

$\displaystyle 7x-130000=150000$

Solving this for $\displaystyle x$ will answer the question.
7x - 130,000 = 150,000

7x = 150,000 + 130,000

7x = 280,000

x = 280,000/7

x = 40,000

P. S. Solving the equation you provided is not the problem. My ongoing struggles with word problems have to do with creating an equation from the written words.

4. ## Re: Number of Items

150000 + 130000 = 280000

Thus:

x = 40000

If x had not been an integer, we would need to round up, since we should assume producing partial units isn't possible.

5. ## Re: Number of Items

Originally Posted by MarkFL
150000 + 130000 = 280000

Thus:

x = 40000

If x had not been an integer, we would need to round up, since we should assume producing partial units isn't possible.
I made a simple division error. Thanks.

6. ## Re: Number of Items

Originally Posted by harpazo
I made a simple division error. Thanks.

7. ## Re: Number of Items

Originally Posted by MarkFL
Solving math problems after working overnight is not easy. I may leave this activity for my days off. This is not an excuse. This is a reality in my life. However, I am slowly coming to the realization that creating an equation from a given application may NEVER sink in. If so, I may stop trying and focus on easier math problems, say, grades 1 to 8....

8. ## Re: Number of Items

Originally Posted by harpazo
Solving math problems after working overnight is not easy. I may leave this activity for my days off. This is not an excuse. This is a reality in my life. However, I am slowly coming to the realization that creating an equation from a given application may NEVER sink in. If so, I may stop trying and focus on easier math problems, say, grades 1 to 8....
Your error was only in the addition, which I know was just a slip, not a lack of understanding of addition. Otherwise your technique for solving was correct.

9. ## Re: Number of Items

Originally Posted by MarkFL
Your error was only in the addition, which I know was just a slip, not a lack of understanding of addition. Otherwise your technique for solving was correct.
I thank you for believing in me. I try to rationalize my way to a reasonable answer in terms of my continued struggles with converting words to algebraic language. For the life of me, I just don't get it!

I know the basic language of algebra as the following three examples will show.

A. The number x is twice y. This converts to x = 2y.

B. A certain number is divided by 100. This becomes x/100.

C. F is 3 more than a certain number. Lastly, this is F = x + 3.

However, when it comes to GMAT, GRE and SAT applications, I am lost in space. Why is this happening? A person that finds time to practice math every given opportunity should not be struggling in this area after more than 20 years.

You read a problem never seen before. You reason your way to the right equation. You never give up. I give up but not right away. I guess life is the way it is. Some people are very good at solving math problems and others hope to be or not to be.

10. ## Re: Number of Items

Originally Posted by harpazo
However, when it comes to GMAT, GRE and SAT applications, I am lost in space. Why is this happening? A person that finds time to practice math every given opportunity should not be struggling in this area after more than 20 years.
I just noticed this. I don't know anything about GMAT but what the heck are you doing looking up problems on both SAT and GRE? The SAT is essentially post High School and the GRE is essentially post college. They are worlds apart in knowledge base!

-Dan

11. ## Re: Number of Items

Originally Posted by topsquark
I just noticed this. I don't know anything about GMAT but what the heck are you doing looking up problems on both SAT and GRE? The SAT is essentially post High School and the GRE is essentially post college. They are worlds apart in knowledge base!

-Dan
I look up GMAT, GRE and SAT questions in terms of word problems. I have two college degrees in areas other than math. Sometimes, I look for GED and ASVAB word problems just for practice. By the way, I passed the ASVAB in 1995 and joined the Navy in April 1996.