Getting Mathematical Errors Trying to calculate base price of gas
Getting Mathematical Errors Trying to calculate base price of gas
I am trying to solve a problem that requires me to write code to find the base price of a gallon of gas. I am provided with the cost of a gallon of gas, the amount of federal and state tax, and the percent for sales tax. I've tried formatting the equation a couple different ways and the math is always wrong. This is the closest I've gotten (the output is $3.289 which is only .073 cents off, which when I do the calculations by hand happens to be the amount of sales tax so it is as if it is ignoring the end of the equation completely). Could I please get some assistance? I've included the entire problem I was given below.
double pumpPrice=3.89, fedTax=.184, stateTax=.417, salesTax=2.25;
double basePrice, totalTax, percentTax, profit_bigOil ;
basePrice = pumpPrice-fedTax-stateTax-((salesTax*basePrice)/100) ;
cout <<"The base price for a gallon of gas is $" <<basePrice << endl;
Create a program, i.e. a Netbeans project with the following inputs
0) Take your pump price, whatever you paid at the pump along with taxes and calculate percentage that you pay in taxes.
Pump Price = Base Price + Fed Tax + State Tax + Base Price * Sales Tax
1) Oil Company Profit -> https://www.forbes.com/2011/05/10/oil-company-earnings.html#6c3f9a9f2dc8
7cents/gallon to 6.5%/gallon
2) Taxes -> http://www.latimes.com/politics/essential/la-pol-ca-essential-politics-updates-california-s-increased-gas-tax-goes-into-1509552219-htmlstory.html
Fed Tax -> 18.4 cents/gallon State Tax -> 41.7 cents/gallon State Sales Tax -> 2.25%
Calculate the following
1) The base price for a gallon of gas = $
2) The total tax on a gallon of gas = $
3) Percentage price due to gas tax = %
4) Oil Company profit range = %
2) Taxes -> latimes.com/politics/essential/… Fed Tax -> 18.4 cents/gallon State Tax -> 41.7 cents/gallon State Sales Tax -> 2.25% Calculate the following 1) The base price for a gallon of gas = $ 2) The total tax on a gallon of gas = $ 3) Percentage price due to gas tax = % 4) Oil Company profit range = %
– Alli Vanzant
Jul 2 at 4:17
Your statement (
basePrice = ...) looks like a mathematical equation. However this is not how C++ (or any other imperative language) works. It needs instructions on how to compute basePrice, not equations. In this case you're using uninitialized basePrice variable in the right-hand side of assignment, which produces undefined behavior– Ap31
Jul 2 at 4:18
basePrice = ...
basePrice
basePrice
Ok, I understand that but then how would I write those instructions?
– Alli Vanzant
Jul 2 at 4:29
Alli, now that you've added the formula, it appears my assumption was correct. What you need to do is just realise that
basePrice + basePrice * salesTaxFraction is the same as basePrice * (1 + salesTaxFraction) (as per the distributive law of algebra). Then you only have one basePrice you need to worry about and the method in my answer will work fine.– paxdiablo
Jul 2 at 4:29
basePrice + basePrice * salesTaxFraction
basePrice * (1 + salesTaxFraction)
basePrice
1 Answer
1
basePrice = pumpPrice-fedTax-stateTax-((salesTax*basePrice)/100) ;
// ^^^^^^^^^ ^^^^^^^^^
That statement is attempting to set basePrice so it's probably a bad idea to use the uninitialised basePrice in the calculation.
basePrice
basePrice
Methinks you need to work out the formula you need to use before translating that into code. A good start would be to take the base price and document how each of the taxes is applied to it to get the pump price. Then it's a simple matter of reversing that process.
For example (and I have no idea if this is actually how you US bods do it with your overly complex tax system), let's say that the base price has sales tax of 2.25% applied, and then the absolute values of state and federal taxes added. That would mean:
pumpPrice = basePrice * (1 + salesTax / 100) + stateTax + federalTax
The reverse of that (working out base price from pump price) would come from:
pumpPrice = basePrice * (1 + salesTax / 100) + stateTax + federalTax
=> pumpPrice - federalTax = basePrice * (1 + salesTax / 100) + stateTax [*a]
=> pumpPrice - federalTax - stateTax = basePrice * (1 + salesTax / 100) [*b]
=> (pumpPrice - federalTax - stateTax) / (1 + salesTax / 100) = basePrice [*c]
[*a] Subtract federal tax from both sides.
[*b] Subtract state tax from both sides.
[*c] Divide both sides by sales tax (adjusted) rate.
And, voila, swap the sides and you have your formula:
basePrice = (pumpPrice - federalTax - stateTax) / (1 + salesTax / 100)
I understand that but I don't see any other way to do it. Maybe my understanding of the question as a whole is wrong.
– Alli Vanzant
Jul 2 at 4:12
I just added a comment with the entire problem
– Alli Vanzant
Jul 2 at 4:13
@AlliVanzant, apologies but, without the actual process used for converting base to pump price, that comment's about as useful as "Given the xyzzy and plugh, calculate the twisty factor" :-)
– paxdiablo
Jul 2 at 4:14
Sorry the entire comment didn't load. I feel like I'm stuck here. I can't get sales tax without base price and can't get base price without sales tax and it just doesn't seem to be doable. I've been trying all weekend
– Alli Vanzant
Jul 2 at 4:19
@AlliVanzant: In your question, you say you're given the sales tax percentage. You only have one unknown, not two.
– ShadowRanger
Jul 2 at 4:30
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Create a program, i.e. a Netbeans project with the following inputs 0) Take your pump price, whatever you paid at the pump along with taxes and calculate percentage that you pay in taxes. Pump Price = Base Price + Fed Tax + State Tax + Base Price * Sales Tax 1) Oil Company Profit -> forbes.com/2011/05/10/oil-company-earnings.html#6c3f9a9f2dc8 7cents/gallon to 6.5%/gallon
– Alli Vanzant
Jul 2 at 4:12