Several years ago, my class tutor expressed frustration after buying an ink cartridge for her printer. “It’s got to be one of the most expensive things in the world,” she said. “It costs more than a vente frappuccino at Starbucks,” she added.

• Was she right? An HP black ink cartridge cost her $20.99 and contained 15 mL of ink (mL = milliliters. There are 1000 mL in 1 Liter). A Starbucks vente cappuccino costs $3.95 for 20 oz.

• Compare the unit price of ink to the cappuccino. Which is more expensive? Show all your calculations.