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mathmat

Discount rates, Formulas

for example, I have 1 computer with a discount, the price of this computer is $ 450 with a 10% discount, I want to know the real price of it, I want to learn this both over 10% and as 10% money.

Computer 10% off Price = 450$
Computer $10 off Price = 490$

$net_total = 450;
$discount_value = 10; < percent or amount
$gross_price =  ?;
Solution

  • Well, let's solve the equations:

    Computer 10% off Price = 450$
Computer $10 off Price = 490$

    Which can be written as (let x be the initial price of the computer)

    x - x * 10 / 100 = 450  # initial price - x without 10 % from x - x * 10% / 100%
x - 10 = 490            # just 10$ off

    Or

    0.9 * x = 450
x = 500

    Finally

    x = 450 / 0.9 = 500
x = 500

    So from both equations we have that the initial computer's price is 500$

    Edit: in general case,

    if $discount_value stands for per cent (i.e. $discount_value = 10 means 10% discount) then

     $gross_price = $net_total * 100.0 / (100.0 - $discount_value)

    if $discount_value stands for money (i.e. $discount_value = 10 means 10$ discount), then

     $gross_price = $net_total + $discount_value