A mad scientist created a shrink ray device that, when used on anything, would cause it to shrink by 50%. The scientist, eager to use his new invention, looked through his house for something to shrink zap. The first thing he found and zapped was his wife, who at the time was carrying a tray containing 5 cups filled with coffee. If each coffee cup held 8 ounces of fluid before being zapped, how many ounces of coffee remained after his wife and the cups filled with coffee were shrink zapped? Let's think first. Chain of thought:
Before the zap, the wife held 5 cups, each with 8 ounces of coffee, for a total of 5 * 8 = 40 ounces of coffee. After the zap, the coffee cups and their contents were shrunk by 50%, for a total of 0.5 * 40 = 20 ounces of coffee.
Therefore, the answer is 20.