Consumer Math

Leslie Green’s Questioncreditcards

The more debt you get into, the more credit card companies profit. If you buy $100 of goods at a shop you owe the credit card company $100, but typically the shop only gets $98. The shop has to inflate its prices to pay the credit card company. Typically the shop is contractually not allowed to give a discount for cash.  The CostCrashers supermarket chain deals only in cash. The CardPayers supermarkets deal with both cash and credit card transactions, although 75% of people pay by credit card.  All else being equal, how much cheaper could the CostCrashers prices be compared to the CardPayers supermarkets, given the figures stated earlier?


Stephen Stead’s Dilemma
Black car
My car uses 10 litres / 100 km and has a 70-litre tank. The Village Garage sells fuel for $1.40 per litre. It is just several meters from my house. Several garages outside the village sell fuel for $1.36 per litre. How far could the garage be so that it is worthwhile to drive to and back from the garage to refuel?



741Bob works 40 years. He does not work on weekends and has a 3-week summer vacation and 7 days of official holidays. The average hourly rate is $12.5 and he works 8 hours per day.  What is his total income?

Stock Price

Every day, a stock price of $444 is either increased or decreased by 4%. When can it be $444 again?


If there is a 500% inflation in a country how much will a 2-dollar telephone cost in one year?


Two successive increases of 25% and 25% are followed by two successive discounts of 25% and 25%.  What percentage is the result?

Selling Luxury Cars

If 2 salesmen can sell three luxury cars in 4 days, how many luxury cars can five salesmen sell to six clients in 7 days?

Ratio 1 : 2 : 3

Divide $132 into a ratio 1:2:3. What are the parts?


Buy 2 for the price of 3 and get 50% off! What is the final rebate do you get?

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