Calculators on smartphones are convenient, but opening them, entering values, and scanning products takes time. Mastering a few mental math shortcuts can make you a faster, smarter shopper. Here are five easy mental math secrets every shopper should know.
1. The Reversibility of Percentages
Did you know that **x% of y is always equal to y% of x**?
If you need to calculate 16% of 50 in your head, reverse the calculation. What is 50% of 16? It is **8**.
This trick works for any percentages. For example, 12% of 25 is equivalent to 25% of 12, which is **3**.
2. The Ten-Percent Base Rule
Calculating a tip, sales tax, or discount is much easier if you establish a **10% base**.
3. Price Rounding and Difference Calculation
When comparing items, round the prices to make calculation easier, and then adjust for the difference.
If an item costs $19.95 and another costs $12.98:
4. Estimation Using Unit Pricing
Retailers often show the unit price (e.g., price per ounce or price per gram) in small font. If this isn't available, you can estimate the unit price to find the best deal.
If a 3-pack costs $4.50 ($1.50 each) and a 5-pack costs $7.00 ($1.40 each), comparing unit prices helps you choose the best option.
5. Double-Checking Bulk Discounts
Don't assume bulk options are always cheaper. Retailers sometimes price larger containers higher per ounce than smaller ones. Doing a quick division or multiplication check on unit pricing can save you money.