Comparing Word Problems

Lesson Plan - Get It!

Audio:

Word problems help us understand how math is used in real life.

Some word problems compare the number of items, the height or weight of an object, or the amount of money someone has. When comparing numbers, if one of the numbers is greater than the other, we need to find the difference. When there is a larger amount compared to a smaller amount, subtract the numbers to find the difference. Subtraction is used to find out how many more, how much greater, how much left, or how many fewer.

In order to subtract two numbers, the largest amount is written first, then the smaller amount is written second, as seen in the example below:

Larger amount - smaller amount = difference. The difference is the answer to a subtraction problem.

Take a look back at the question from the start of the lesson:

Sarah’s basket had 500 cherries. Timmy’s basket had 200 cherries. How many more cherries did Sarah have?

Some subtraction word problems have an amount that “went away.” An example of a "went away" problem would be: "Sarah had 400 cherries in her basket. She used 200 cherries to make a pie. How many cherries does she have left?"

In this story, we are comparing two numbers. When we compare numbers, the smaller number is subtracted from the larger number. The difference, or the answer, tells us “how many more.” Since Sarah had more cherries than Timmy, we have to subtract.

500 - 200 = 300 cherries. There were 300 fewer cherries in Timmy’s basket.

Let’s look at another example:

27 apples is how many fewer than 85 apples?

The important words in this problem are “how many fewer." The pattern is the same for finding “how many more.” Use a subtraction pattern to compare the numbers by subtracting the smaller number from the larger number.

85 - 27 = 58

Don’t forget to borrow! 27 apples is 58 apples fewer than 85 apples.

Here's another example:

Sixteen is how much less than 39? What important phrase in this example tells us to subtract? Discuss with a parent or teacher.

Problems about numbers that ask “how much less” or “how much greater” are also subtraction problems. This time, we have to change the word “sixteen” to the number “16” before subtracting.

39 - 16 = 23

Sixteen is 23 less than 39.

Discuss with a parent or teacher:

• What are two of the special phrases tell us to subtract in word problems?
• When subtracting, does the larger or smaller number go first? Why do you think this is?

Now, move on to the Got It? section to practice solving subtraction word problems.