Selling Price after a 21% Markup is applied to an item that Cost $20

Given: Cost = $20,  Markup = 21%
Markup as a Decimal: 21% = 0.21
Formula:
Selling Price = Cost * (1 + Markup as a Decimal)
Selling Price = $20 * (1 + 0.21)
Selling Price = $20 * 1.21
Selling Price = $24.20
Notes:
Markup Amount = Selling Price – Cost = $24.20 – $20 = $4.20
Profit = Markup Amount = $4.20
Profit Margin =   =   = 0.1736 = 17.36%