Think about people older than you. How would you write a problem showing how much older your friend is? When a comparison word problem asks about the difference (answer) between two things, we set up and solve the problem using number families.

Look at this example: How much older is Martha than Grace? Since Martha is older, Martha equals the greatest (larger) number and Grace equals the lesser (smaller) number. The sentence asks, how much older? We write a box for "how much."

Here's another word problem: The tree Lourdes planted is 60 inches tall. The tree Elsa planted is 74 inches tall. How much shorter is the tree Lourdes planted? The last sentence of the comparison problem tells us how to make the number family. Since the tree Lourdes planted is shorter, Lourdes, or the variable L, equals a lesser number. Elsa, or the variable E, will equal the greatest number. "How much" is put in a box.

The first sentence tells us that the tree Lourdes planted is 60 inches tall. So we replace L with 60. The next sentence says that the tree Elsa planted is 74 inches tall. We replace E with 74.

Now we can write the subtraction problem. Our answer is 14.




 When you work on word problems, remember to write the unit name in the answer. The unit name in the answer is inches.

The tree Lourdes planted is 14 inches shorter than the tree Elsa planted.