Posted by davie on 09/01/06 08:09

universalbitmapper wrote:
> Hi,
>
> I'm coding a PHP/MySQL application.
> I'm looking for the formula to compute the original variable after it
> has been applied VAT.
> For instance 100 + 18% -> 118.
> But if I try to find out 100 from 118 - 18%, the result is greater than
> 100.
> I don't have enough maths background to solve the equation:
> c = a + (a*b/100)
> I'm stuck at this point:
> a = (a*b/100) -c
> I would like to have all 'a' on the left side and b and c on the right.
>
> Can someone help?
We know that the selling price of £1 560 is 130% of the cost price
since the dealer is making a profit of 30% on the cost price. So we can
say
£1 560 = 130/100 + cost price
Now multiply both sides of this equation by 100 and divide both sides
by 130. This gives
100/130 X £1 560 = 100/130 X 130/100 + cost price = cost price
Since the two right-hand fractions cancel each other out.
Therefore the cost price to the dealer was £156 000/130 = £1 200.

ie 118000/118= 100

[Back to original message]