The Better Buy
Part of the Decimals, Percents & Ratios section of Coddy's Pre-Algebra journey. Lesson 43 of 56.
A shop sells pens in two packs: 4 pens for 2.80 dollars, or 10 pens for 6.50 dollars. Which is the better buy? The totals cannot be compared directly, because the packs hold different numbers of pens. So find the price of ONE pen in each, the unit price.
Small pack: 2.8 / 4 is 0.7, so 70 cents a pen. Large pack: 6.5 / 10 is 0.65, so 65 cents a pen. Both prices are now for the same thing, one pen, and the smaller unit price is the better buy: the large pack, even though its total is higher.
Divide the price by the count, in that order. Dividing the count by the price gives pens per dollar instead, where the bigger number is the better buy, and mixing the two up flips the answer. A better buy is only better if you will use what you buy, but that part is up to you.
Challenge
A box of 12 pencils costs 3.60 dollars. Find the price u of one pencil, so the box can be compared with other packs. Write u equal to the calculation, then work it out on the next line.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Decimals, Percents & Ratios
4Dividing Decimals
Dividing by a DecimalDividing by 10 and 100Dividing by a Whole NumberUnit PriceRecap: Dividing