Adding and subtracting/multiplying fractions

• Wiskunde
• Middelbare school
• vwo
• Leerjaar 2

Good morning!

Schedule: 

• Learning goals
• Last time
• Adding/subtracting fractions
• Multiplying fractions
• Work/practice

Learning goals 

At the end of this lesson I can:

• add any fraction to another fraction 
• subtract any fraction from another fraction
• Do multiplications with proper fractions
• Do multiplications with mixed numbers and improper fractions

Last time

​2​​1​​+​6​​3​​=

1. ​8​​4​​
2. ​12​​3​​
3. ​2​​2​​

Equal fractions

​2​​1​​=​6​​3​​

When am I allowed to add or subtract fractions?

Adding/subtracting fractions

Same denominator!! 

​6​​2​​+​6​​1​​=

​3​​1​​+​9​​2​​=

​7​​5​​−​8​​3​​=

Multiplying fractions

Multiplying fractions

​3​​1​​⋅​5​​2​​=​3⋅5​​1⋅2​​=​15​​2​​

Numerator x numerator 

Denominator x denominator

Mixed numbers/whole numbers?

What is the difference between multiplying and adding/subtracting fraction?

Adding fractions

How can thinking about the context of a problem help you in

understanding the situation and what the question is asking you to solve? How can this

help you to determine a way to solve this problem?

Discuss with neighbour (2min)

A school uses part of a field to create a rectangular area for the PTA carnival. They will partition the field so there are areas for games, food, and prizes. If      of the field is for prizes, and     of the field is for games, what fraction of the field is remaining for food?

How can the context/story of the problem help you solve it? what strategy would you use?  

Discuss (5 min) 

​2​​1​​

​6​​1​​

A school uses part of a field to create a rectangular area for the PTA carnival. They will partition the field so there are areas for games, food, and prizes. If      of the field is for prizes, and     of the field is for games, what fraction of the field is remaining for food?

Think of a reasonable estimate for the answer to the question. Write this down on your mini-whiteboard. 

Discuss (5 min) 

​2​​1​​

​6​​1​​

What do you think? 

a. The answer is less than 1.

b. The answer is more than

 

c. The answer is less than 

d. The answer is more than 0.

e. The answer is closer to 0 than 

​2​​1​​

​2​​1​​

​2​​1​​

Now find the exact answer to the problem:

Adding/subtracting fractions

You changed 1/2 into 3/6 

When you add 2 fractions you need to change them to make the denominators equal 

https://www.geogebra.org/m/d4sq3jzx

(Home)work

Worksheet on ManageBac: 1-10

p. 113 : 5H                1bfjcgk, 2aei, 3, 4be, 5

Finished? Challenge worksheet!

MyiMaths:

- adding and subtracting fractions

Challenge