Subtracting to Solve Word Problems

Subtraction……. Order matters!!!!!!!! We are not able to rearrange the values to solve! Proper fractions may be written horizontally or vertically. We will use the vertical form to work with mixed numbers.

Three and one-fourth feet are cut off of a board that is twelve and one-third feet long. How long is the remaining part of the board? Order matters!!!! Think about what the problem is saying as you begin to solve! We are writing mixed number subtraction problems vertically for a reason! Practice this process correctly!

Borrowing in Subtraction As you know, order matters in subtraction. Sometimes we have to borrow from the “first” whole number in order to subtract the fraction in the problem. In our first examples, we will write a whole number as a mixed number.

Process Example Jerri has read 14 books. Her brother has read 4 ¾ books. How many more books has Jerri read? We will have to borrow “one” from our 14 so we can subtract the fraction. We will write this one that we borrow in fourths……we have to have a common denominator!

If 3 ½ ounces of cough syrup is used from an 8 ounce bottle, how much cough syrup is left?

What have we accomplished? In the first part of this lesson we have subtracted fractions from other fractions. We have also regrouped with whole numbers so we could subtract other fractions and mixed numbers.

Review and Extend Yesterday we subtracted mixed numbers and regrouped with whole numbers. Today we will extend this idea and regroup with mixed numbers. These problems have THREE sections: ProblemRewritten Problem (LCD)Regrouped Problem

Regrouping in Subtraction The next two examples will have mixed numbers that will be regrouped during the borrowing process. This involves several steps. We will discuss these steps, and you will also see a great shortcut for the new fraction in the problem! Be patient.

Process Example First we need a common denominator!!! Now we can see that we have to borrow! 4 + what we had Let’s go back to the step where we regroup. We borrow from the 4, leaving a whole number of

5 Borrow from the 6

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Group Practice Jesse bought 8/9 of a pound of chocolates and ate 1/3 of a pound. How much was left?

Please add this problem to your notes.

What did we accomplish? We solved three types of subtraction word problems. We practiced borrowing from a whole number as well as regrouping within a mixed number to successfully solve the problems!