Overview

Temporal data is the hardest type of data for people to handle conceptually. Perhaps time is difficult because it is dynamic and all other data types are static, or perhaps it is because time allows multiple parallel events. This is an old puzzle that still catches people. If a hen and a half can lay an egg and a half in a day and a half, then how many hens does it take to lay six eggs in six days? Do not look at the rest of the page; try to answer the question in your head.

The answer is a hen and a half although you might want to round that up to two hens in the real world. People tend to get tripped up on the rate (eggs per hen per day) because they handle time incorrectly. For example, if a cookbook has a recipe that serves one, and you want to serve 100 guests, you increase the amount of ingredients by 100, but you do not cook it 100 times longer.

The algebra in this problem looks like this, where we want to solve for the rate in terms of "eggs per day," a strange but convenient unit of measurement for summarizing the hen house output:

1<sup1</sup>/2 hens * 1<sup1</sup>/2 days * rate = 1<sup1</sup>/2 eggs 

The first urge is to multiple both sides by in an attempt to turn every 1 ¹