Transcript Please be prepared.

Please copy your Agenda for the week: Sept 14-18.
Multiplying Fractions and Mixed
Numbers
CCSS.5NS.4 Multiply a whole number or fraction by a fraction.
CCSS.6.NS.1 Multiplying fractions…real world problems.
Essential Questions:
Why would it be useful to know the greatest common factor of a set of
numbers? What kind of models can I use to show solutions to word
problems involving fractions?
You will need your Math Journal open to the next clean page,
a pencil, a red pen, 2 colored pencils, a highlighter, and glue.
Let’s discuss common errors made
on the last quiz!
Please fold your quiz in half and glue it into your
Journal. Use your red pen to correct your errors on
your quiz.
WARM UP: Think back to what you
have learned about multiplying
fractions to help Mark.
 Mark is finding ¾ of 8. Find his mistake and correct it.
𝟑
𝟒
x8=
𝟐𝟒
𝟑𝟐
 Mark is finding ¾ of 8. Find his mistake and correct it.
 Mark multiplied by
3
4
x
8
1
=
𝟑
𝟒
24
4
x8=
8
instead
8
=6
𝟐𝟒
𝟑𝟐
Oops!
of multiplying by
8
.
1
Review: Multiplying whole numbers
and fractions:
 Write the whole number as an improper fraction. Then
multiply the numerators, multiply the denominators, and
simplify if possible. Or simply multiply the whole number
by the numerator, the denominator stays the same. Simplify.
 EX. 4 x
 5x
 5x
2
3
2
3
=
 Solve: 8
 8x
2
5
=
2
3
=
4
1
10
3
=3
2
3
8
3
x = =2
1
3
2
x
5
16
1
=3
5
5
2
3
Review: Multiplying fractions. Write
this in your Journal!
 Multiply the numerators, multiply the denominators, and
simplify if possible.
 Rick has
1
2
1
3
of a footlong sub left from yesterday. He ate of
the leftover sandwich as a snack. What fraction of the entire
sandwich did he eat as a snack?
1
2
x
1
3
1
6
= of the sandwich
Simplify before multiplying using the
GCF… Write this in your Journal!
 If the numerators and the denominators have a common
factor you can simplify before you multiply. If you cancel
all the common factors using the GCFs before
multiplying, the product will be in lowest terms. (Use 2
colored pencils for the example.)
5
6
x
9
10
=
45
60
=
3
4
Simplify before multiplying using the
GCF… Write this in your Journal!
 If the numerators and the denominators have a common
factor you can simplify before you multiply. If you cancel
all the common factors using the GCFs before
multiplying, the product will be in lowest terms.
1
5
6
2
3
x
9
10
2
3
=4
Practice this skill:
1. Glue the handout “A Shortcut for Multiplying Fractions”
into your Math Journal.
2. Complete all work in your Journal. Show all steps, even if
you can solve it mentally. 
 Due tomorrow.
Sept. 15
Please have your HW ready to grade.
You need: Journal open to HW, red pen, pencil,
highlighter…the usual…you need these items every
day.
Essential Question:
Why would it be useful to know the greatest
common factor of a set of numbers?
Copy into your Journal:
Review: Writing Mixed Numbers as
Improper Fractions
 Multiply the whole number part and the denominator, add
the numerator, and write the sum over the denominator.
 Numbers: 1 ¾ = 4 x 1 + 3 = 7
4
4
Writing Improper Fractions as
Mixed Numbers Write this in your
Journal!
 Divide the numerator by the denominator and write any
remainder as a fraction.
 Numbers:
9
2
means 9 ÷ 2 = 4 r1 of 2, or 4 ½
Giant Squid…oh, my!!
Focus: Giant Squid Eye!
 The eyeball of an Atlantic Giant Squid is about 12 times as large
as the average human eyeball. The average human eyeball is 1
¼ inches across. Use a bar diagram to compare the average
size of a human eyeball to the average size of an Atlantic Giant
Squid’s eyeball.
|- - - - - - - - - - - - - - - - -squid eyeball- - - - - - - - - - - - - - -|
1¼
1¼ 1¼ 1¼ 1¼
1¼
1¼
1¼
1¼
1¼
1¼
1¼
|- - -|
Human eyeball
 Use the diagram above to compare the average size of the Atlantic
Giant Squid’s eyeball to the average size of the human eyeball. Use
repeated addition.
Focus: Giant Squid Eye!
 |- - - - - - - - - - - - - - - - -squid eyeball- - - - - - - - - - - - - - -|
1¼
1¼ 1¼ 1¼ 1¼
1¼
1¼
1¼
1¼
1¼
1¼
1¼
|- - -|
Human eyeball
 Use the diagram above to compare the average size of the Atlantic
Giant Squid’s eyeball to the average size of the human eyeball. Use
repeated addition.
 Write a multiplication expression that shows the size of the Atlantic
Squid’s eyeball.
 Write the multiplication expression using improper fractions.
Multiply to find the size of the squid’s eyeball.
Multiplying Mixed Numbers and
fractions…You will highlight this on your
handout shortly.
 First write the mixed number as an improper fraction.
Remember that when mixed numbers are written as
improper fractions, the denominator does not change.
 Then multiply as with fractions.
 Simplify if possible.
 EX. 2 ½ x ¼ =
5
2
1
4
x =
5
8
Multiplying Mixed Numbers
 EX. The Hoover Dam contains 4
1
2
million cubic yards of
concrete. The Grand Coulee Dam, in Washington State,
2
3
contains 2 times as much concrete. How much concrete
does it contain?
Left/Center/Right
 Is the product of two mixed numbers greater than or less




than both of the factors?
Move to the LEFT of the room if you think it is greater than.
Move to the RIGHT of the room if you think it is less than.
Move to the CENTER of the room if you think it depends on
the mixed numbers.
BE ABLE TO JUSTIFY WHERE YOU MOVE.
HOMEWORK
 Complete the practice worksheet “Multiplying Mixed
Numbers Independent Practice”. Due tomorrow. You will
have a quiz Friday over adding, subtracting, and multiplying
fractions.
 Thursday will be a practice day to review all of these skills.
Come prepared to ask questions about skills you may be
having a challenge with.