Consumer Arithmetic

Section 1What consumer arithmetic is

Consumer arithmetic is mathematics for buying, selling, and comparing prices. It includes discounts, sales tax, profit, loss, markup, and final prices. In plain words, this is the maths behind supermarket receipts, school fairs, small shops, and online deals.

Section 2Discount

A discount is a reduction from the marked price or original price. To find the sale price, calculate the discount amount, then subtract it from the original price. This is one of the most common exam slip-ups: students find the discount amount and forget the final subtraction.

Section 3Sales tax

Sales tax is an extra percentage added to the selling price of some goods and services. In Jamaica, you may see this idea on receipts as GCT, but an exam question will give the rate to use. To find the tax-inclusive price, calculate the tax amount, then add it to the price before tax.

Section 4Cost price, selling price, profit, and loss

Cost price is what the seller paid for an item. Selling price is what the customer pays. Profit happens when selling price is greater than cost price, and loss happens when selling price is less than cost price. Here's the trick: profit or loss is the difference between selling price and cost price.

Section 5Profit and loss percentages

Profit percent and loss percent are usually calculated using cost price as the base. Profit percent = profit / cost price x 100%. Loss percent = loss / cost price x 100%. Watch out: using selling price as the denominator gives the wrong CSEC-style answer unless the question specifically asks for that.

Section 6Markup

Markup is the amount added to cost price to set a selling price. If a shop buys a bag for J$3000 and adds a 20% markup, the markup is 20% of J$3000, which is J$600. The selling price is J$3600.

Section 7Choosing the right calculation

Read the question for direction words like reduced by, increased by, added tax, sold for, cost price, and selling price. Easy to mix up - discount reduces a price, while sales tax and markup increase it. A quick estimate helps you check whether the final answer moved in the right direction.