Need urgent help with simple Math problem

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JBGin2020

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Hi I need your help. I have this simple Maths problem but I got stuck.

This is the problem:

I need to set a value price for a product, but I will be taxed 3.9% and I have to end up with 140 dollars at the end.

The 3.9% is a constant

The 140 is a constant

the only variable is the starting price, the price that I will have to charge in order to after the tax fee of 3.9% I will end up with 140.


I believe that the equation is

x - 3.9% = 140


but I may be wrong. I also couldn't get the value of x right.

Can you help me please?

Thank you
 
JBGin2020 said:
Hi I need your help. I have this simple Maths problem but I got stuck.
This is the problem:
I need to set a value price for a product, but I will be taxed 3.9% and I have to end up with 140 dollars at the end.

The 3.9% is a constant

The 140 is a constant

the only variable is the starting price, the price that I will have to charge in order to after the tax fee of 3.9% I will end up with 140.
I believe that the equation is

x - 3.9% = 140

but I may be wrong. I also couldn’t get the value of x right.

Can you help me please?
Thank you
Click to expand...
You have not "explicitly" defined your variable 'x'. Reading your work - it looks like you want to say:

x = selling price of the item ( this is a correct thought)

tax rate = 3.9% = 3.9/100 = 0.039

so tax charged = 3.9% of the selling price = 0.039 * (the selling price) = 0.039 * x....... (this goes to the government)

Money you want to make = 140

Now if I write the required condition of making a mathematical statement:

Selling price = (Money you want to make) + (tax charged), or

x = 140 + 0.039 * x

x - 0.039 * x = 140

continue.......
 
JBGin2020 said:
Hi I need your help. I have this simple Maths problem but I got stuck.

This is the problem:

I need to set a value price for a product, but I will be taxed 3.9% and I have to end up with 140 dollars at the end.

The 3.9% is a constant

The 140 is a constant

the only variable is the starting price, the price that I will have to charge in order to after the tax fee of 3.9% I will end up with 140.


I believe that the equation is

x - 3.9% = 140
Click to expand...
This doesn't even make sense! In the first place a percentage is not really a number so you cannot add or subtract "3.9%". Second, a percent is always "a percent of something" You need to convert "3.9%" to \(\displaystyle \frac{3.9}{100}= 0.039\) and then, because the tax is "3.9% of the price", subtract 0.039x, not just "3.9%".

You need to solve the equaton x- 0.039x= (1- 0.39)x= 0.61x= 140.

but I may be wrong. I also couldn't get the value of x right.

Can you help me please?

Thank you
Click to expand...
 
Can you please tell me what for example 125 - 3.9% equals?
 
Thank you for your help I got your idea, it makes sense, so what is the final result? what is the value of x. Is it = 0.039??
But if we do 140.039 - 3.9% it is not = to 140. Or I may be confused.
 
JBGin2020 said:
Thank you for your help I got your idea, it makes sense, so what is the final result? what is the value of x. Is it = 0.039??
Click to expand...


No. Solve the equation (from post #4):

0.961x = 140

The value of x is the selling price for the product.
 
JBGin2020 said:
Thank you for your help I got your idea, it makes sense, so what is the final result? what is the value of x. Is it = 0.039??
But if we do 140.039 - 3.9% it is not = to 140. Or I may be confused.
Click to expand...
No, you can't subtract a percentage from a number. Actually you can but the result will have no meaning.

For example, if an item you want to buy cost $10 and the sale tax is 10% then you are saying that 10 + .10 = $10.10. OK, I will work with that.
Now if an item you purchase cost $20, then you will pay 20 + .10 = $20.10. Ah, I get it. The sales tax is always $.10. This is not true! It doesn't work that way.

I also made a mistake above. The 10 had units, it was $. But the 10% has no units. They can not be added.

So how is it done? The answer is you need to compute 10% of something. In my case that something is the price of the item.

Now $10 + 10%*$10 = $10 + $1 = $11.
$20 + 10%*$20 = $20 + $2 = $22
 
JBGin2020 said:
So the price should be $145.682 right? That was my result.
Click to expand...
I would think not. If I understood your original problem you want to know the price that when you add on the sales tax will give you $140.

Clearly you need to add sales to an amount less than $140 for any hopes that the sum will be $140.

If you ADD sales tax to $145.682 then the result will be more than $145.682 and hence larger than $140. Is this clear??
Subhotosh Khan said:
You have not "explicitly" defined your variable 'x'. Reading your work - it looks like you want to say:

x = selling price of the item ( this is a correct thought)

tax rate = 3.9% = 3.9/100 = 0.039

so tax charged = 3.9% of the selling price = 0.039 * (the selling price) = 0.039 * x....... (this goes to the government)

Money you want to make = 140

Now if I write the required condition of making a mathematical statement:

Selling price = (Money you want to make) + (tax charged), or

x = 140 + 0.039 * x

x - 0.039 * x = 140

continue.......
Click to expand...
Read the problem again!
 
Because Subhotosh Khan did not read the problem carefully and confused you, I will work out the problem for you.

Let x = the price you should charge so that after the sales tax it will cost $140.

The total cost ($140) comes from the sale price plus the sales tax.

Hence 140 = x + .039x

140 = 1.039x

x = $140/1.039 = $134.7449

So you should charge either $134.74 or $134.75 .............. This solution is incorrect due to misinterpretation of "conditions" in OP.
 
Last edited by a moderator:
It is quite clear to me that the OPer wants exactly $ 140 to their credit after all transactions have been completed. They charge $ 145.68 for their item. Tax @ 3.9%, $ 5.68, is passed the government / state, the OPer is left with the $ 140.00 they want.
 
I have read the problem over five times. There is enough ambiguity in the English
that I would ask the instructor for a clarification on the phrase "will be taxed."
If it were a sales tax question for sure, it would not be an issue.
 
OK, OK I misread the problem. Please understand that it is dark in the corner so it is understandable how I can make the mistake I made.
 
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