simple math question

[vital]

what's the formula to figure out subtotal before tax when the after tax total and tax rate is given?

for example, if the total is $135.75 and tax is 7.75%, how much is the subtal before tax?

 

[Heisenberg]

135.75 - (0.0775*135.75)

Edit: Should be x+x*0.0775=135.35. I really do have a math minor, honest.

 

[vital]

Originally posted by: Heisenberg
135.75 - (0.0775*135.75)

0.0775*135.75 would give you the tax of the $135.75 (aftertax) not the subtotal..

 

[czech09]

Originally posted by: vital

Originally posted by: Heisenberg
135.75 - (0.0775*135.75)

0.0775*135.75 would give you the tax of the $135.75 (aftertax) not the subtotal..

Correct. That's what I thought you were asking as well in the first place.

 

[czech09]

92.25%=135.75 so 100%=xjust a simple cross multiplication problem.

 

[stan394]

Originally posted by: vital
what's the formula to figure out subtotal before tax when the after tax total and tax rate is given?

for example, if the total is $135.75 and tax is 7.75%, how much is the subtal before tax?

so x * (1 + 0.0775) = 135.75

 

[czech09]

Originally posted by: stan394

Originally posted by: vital
what's the formula to figure out subtotal before tax when the after tax total and tax rate is given?

for example, if the total is $135.75 and tax is 7.75%, how much is the subtal before tax?

so x * (1 + 0.0775) = 135.75

Yup that works too as well as my way it's 147.15 or so...

 

[Ilmater]

sub-total=(total)/(1+tax rate)

 

[QED]

Originally posted by: vital
what's the formula to figure out subtotal before tax when the after tax total and tax rate is given?

for example, if the total is $135.75 and tax is 7.75%, how much is the subtal before tax?

Just divide the total by 1 + the tax rate:

$135.75
-------- = $125.99
1.0775

 

[vital]

Originally posted by: MathMan

Originally posted by: vital
what's the formula to figure out subtotal before tax when the after tax total and tax rate is given?

for example, if the total is $135.75 and tax is 7.75%, how much is the subtal before tax?

Just divide the total by 1 + the tax rate:

$135.75
-------- = $125.99
1.0775

that's it, thanks

 

[Fiveohhh]

Originally posted by: MathMan

Originally posted by: vital
what's the formula to figure out subtotal before tax when the after tax total and tax rate is given?

for example, if the total is $135.75 and tax is 7.75%, how much is the subtal before tax?

Just divide the total by 1 + the tax rate:

$135.75
-------- = $125.99
1.0775

That was my thinking as well.

x+x*.0775=135.76
x(1+.0775)=135.76
x=135.76/1.0775

 

[Heisenberg]

Originally posted by: vital

Originally posted by: Heisenberg
135.75 - (0.0775*135.75)

0.0775*135.75 would give you the tax of the $135.75 (aftertax) not the subtotal..

Whoops. 😱 Yeah, the correct expression would be x+x*0.0775=135.75, solve for x. Stupid misfiring neuron...

 

[InlineFour]

here's the equation:

135.75 = x + 0.0775x

combine like terms and solve for x.

 

[Mday]

most ppl just do this:

tax rate = T%

"pre tax price" * (1+T%) = "after tax price"

So if you buy a $100 item, and the tax rate is 8%, you get

$100 * 1.08 = $108

To get the pre tax price:

"pre tax price" = "after tax price" / (1+T%)

So, if you paid $108 for an item, and the rate is 8%, you get

$108 / 1.08 = $100