Cost of an item given Selling Price of $20 and a 100% Markup on Cost

Given: Selling Price = $20,  Markup = 100%
Markup as a Decimal: 100% = 1
Formula:
Cost =  

Selling Price/ 1 + Markup as a Decimal

Cost =  

$20/ 1 + 1

Cost =  

$20/ 2

Cost = $10
Notes:
Markup Amount = Selling Price – Cost = $20 – $10 = $10
Profit = Markup Amount = $10
Profit Margin =  

Profit/ Selling Price

=  

$10/ $20

= 0.5 = 50%