You already know how to write comparison word problems using number families. Solving them is just as easy. Do you remember the steps?
Let us practice with this problem: Cherry has more pencils than Libby. Who is the greatest (larger) number? Since Cherry has more pencils than Libby, Cherry equals the greatest number. Only the lesser (smaller) numbers are left. That means Libby equals one lesser number. We use the first letters of the two names to write our number family:
When our comparison problem asks about the difference (answer) between two things, we solve the problem by using the number families. Let's look at this example first:
Jack has 65 marbles. He plans to give 20 of them to Greg. How many marbles will Jack have left?
How do we solve this problem? Since Jack is giving away marbles, we subtract:
Jack will be left with 45 marbles. When you work on word problems, remember to write the unit name in the answer. In our example, the unit is marbles.
Look at this example: How much older is Sally than Bill?
The sentence tells us that one person is older. So who's older? Sally is older. She equals the greatest number. Bill equals the lesser number.
The sentence asks, how much older? What do we write for "how much"? We write a box for "how much." Now write the number family for this comparison problem.
