unit 3: fractions 3.8 solving problems with fractions

Unit 3: FractionsUnit 3: Fractions

3.8 Solving Problems with Fractions3.8 Solving Problems with Fractions

A grade 8 class is going to a canoe A grade 8 class is going to a canoe competition. There are 24 students in the competition. There are 24 students in the class. Each canoe holds 4 people. How class. Each canoe holds 4 people. How many canoes does the class need? How many canoes does the class need? How did you know what operation to use?did you know what operation to use?

Look at the example on pg 147 in your Look at the example on pg 147 in your textbook. textbook.

Answer the four questions on loose leaf. Answer the four questions on loose leaf.

When working with word problems, key When working with word problems, key words and phrases can help identify the words and phrases can help identify the operation or operations needed to solve operation or operations needed to solve the problem. the problem.

Operations include adding, subtracting, Operations include adding, subtracting, multiplying, and dividing. multiplying, and dividing.

In order to identify the In order to identify the operation:operation:

1.1. Think about the situationThink about the situation

2.2. Make sense of the problem by Make sense of the problem by explaining it in your own words, drawing explaining it in your own words, drawing a picture, or using a model. a picture, or using a model.

3.3. Think about what is happening in the Think about what is happening in the problem. Sometimes key words can problem. Sometimes key words can help you identify the operation to use. help you identify the operation to use.

Key words:Key words:

““total” suggests addingtotal” suggests adding ““less than” suggests subtractingless than” suggests subtracting ““times” suggests multiplyingtimes” suggests multiplying ““shared” suggests dividingshared” suggests dividing ““of” suggests multiplyingof” suggests multiplying

Although key words may help identify an Although key words may help identify an operation, the operation must make sense in operation, the operation must make sense in the context of the problem. the context of the problem.

Kassie worked on her science project for Kassie worked on her science project for ¾ h on Tuesday and 5/6 h on ¾ h on Tuesday and 5/6 h on Wednesday. She spent Thursday Wednesday. She spent Thursday finishing her math homework. finishing her math homework.

A) How long did Kassie work on her A) How long did Kassie work on her science project all together?science project all together? ““altogether” suggests addingaltogether” suggests adding Add ¾ and 5/6 Add ¾ and 5/6

B) How much longer did Kassie work on B) How much longer did Kassie work on the project on Wednesday than on the project on Wednesday than on Tuesday?Tuesday? The words “longer…than” suggest The words “longer…than” suggest

subtraction.subtraction. 5/6 – ¾ 5/6 – ¾

C) Altogether, Kassie spent 2 h on school C) Altogether, Kassie spent 2 h on school work over the 3 days. How long did work over the 3 days. How long did Kassie spend on her math homework?Kassie spend on her math homework? ““altogether” suggests addition; however, to altogether” suggests addition; however, to

find the time Kassie spent doing math find the time Kassie spent doing math homework, we subtract. homework, we subtract.

2 – 1 7/122 – 1 7/12