Percentages: Not a php question, but still...

Collapse
This topic is closed.
X
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • universalbitmapper
    #1

    Percentages: Not a php question, but still...

    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?

    Tags: None
    • davie
      #2
      Re: Percentages: Not a php question, but still...

      universalbitmap per 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

        Comment

        • Kimmo Laine
          #3
          Re: Percentages: Not a php question, but still...

          "universalbitma pper" <jbmorla@gmail. comwrote in message
          news:1157093880 .725466.161370@ h48g2000cwc.goo glegroups.com.. .
          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?

          Short answer:
          100 / (100+VAT) * price with VAT = original price
          100 / (100+18) * 118 = 100

          I don't know the correct mathematical terms, but basicly this is what
          happens:
          the ratio of 100 : (100 + VAT) must be the same ratio as "original price" :
          "VAT price"
          100 / (100 + VAT) = original price / VAT price
          multiply both sides with VAT price:

          ==100 / (100 + VAT) * VAT price = original price * (VAT price/VAT price)
          ==100 / (100 + VAT) * VAT price = original price

          there you have it.

          --
          "Ohjelmoija on organismi joka muuttaa kofeiinia koodiksi" - lpk
          http://outolempi.net/ahdistus/ - Satunnaisesti päivittyvä nettisarjis
          spam@outolempi. net || Gedoon-S @ IRCnet || rot13(xvzzb@bhg byrzcv.arg)


            Comment

            • usenet+2004@john.dunlop.name
              #4
              Re: Percentages: Not a php question, but still...

              universalbitmap per:
              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.
              Yes, because 18 % of 118 is greater than 18 % of 100, so 118 minus 18 %
              of 118 is over 100.

              Given your figures, you are trying to find x in

              118/x = 118/100

              that is, your figure after tax (118) divided by your figure before tax
              (x) equals your tax rate(118 % not 18 %) divided by 100.

              Multiplying both sides by 100,

              =11800/x = 118

              =118x = 11800

              =x = 100

              ObOT: "Standard" VAT in the UK is 17.5 %, no?

              --
              Jock

                Comment

                • usenet+2004@john.dunlop.name
                  #5
                  Re: Percentages: Not a php question, but still...

                  usenet+2...@joh n.dunlop.name:
                  universalbitmap per:
                  >
                  But if I try to find out 100 from 118 - 18%, the result is greater than
                  100.
                  >
                  Yes, because 18 % of 118 is greater than 18 % of 100, so 118 minus 18 %
                  of 118 is over 100.
                  Scrub that. Should be 'under 100'.

                  18 % of 118 is 21.24. The result is less than 100.

                  --
                  Jock

                    Comment

                    • davie
                      #6
                      Re: Percentages: Not a php question, but still...

                      universalbitmap per 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

                        Comment

                        • Kimmo Laine
                          #7
                          Re: Percentages: Not a php question, but still...

                          <usenet+2004@jo hn.dunlop.namew rote in message
                          news:1157098770 .725070.277100@ i42g2000cwa.goo glegroups.com.. .
                          >
                          ObOT: "Standard" VAT in the UK is 17.5 %, no?

                          Who said anything about UK? There ARE other countries. :)

                          --
                          "Ohjelmoija on organismi joka muuttaa kofeiinia koodiksi" - lpk
                          http://outolempi.net/ahdistus/ - Satunnaisesti päivittyvä nettisarjis
                          spam@outolempi. net || Gedoon-S @ IRCnet || rot13(xvzzb@bhg byrzcv.arg)


                            Comment

                            • Petr Vileta
                              #8
                              Re: Percentages: Not a php question, but still...

                              "universalbitma pper" <jbmorla@gmail. comwrote in
                              news:1157093880 .725466.161370@ h48g2000cwc.goo glegroups.com.. .
                              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?
                              >
                              price_without_w at = price_incl_vat / (100 + vat) * 100

                              In your example: 100 = 118 / (100 + 18) * 100

                              --

                              Petr Vileta, Czech republic
                              (My server rejects all messages from Yahoo and Hotmail. Send me your mail
                              from another non-spammer site please.)


                                Comment

                                Previous template Next
                                Working...