With 20% off, you save one-fifth of the original price. On a $200 item, that's a $40 savings, bringing the price down to $160. The higher the original price, the more significant your dollar savings become with a 20% discount.

Find 10% by moving the decimal one place left, then double it. For a $200 item, 10% is $20, so 20% is $40. Subtract $40 from $200 to get the sale price of $160. This two-step mental math trick works for any price.

It depends on the price of the item. For items over $100, a 20% discount saves you more than a flat $20 off. For items under $100, the flat $20 off is the better deal. At exactly $100, both discounts are equivalent.