Transcript Document

Chapter 7 lesson 1
0011 0010 1010 1101 0001 0100 1011
1
cjm12/28/2012
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4
Multiplying whole numbers and
fractions
4/5 of 20 is the same as 4/5 x 20 or
20 x 4/5
0011 0010 1010 1101 0001 0100 1011
• How
• Using 20 counters,
divide them into 5
groups.
• Circle 4 groups
(4/5)
• How many
counters are
circled?
16
many
are in
each
group?
2
14
4
4/5 x 20=16
Example (pg 292)
2/3 of 12 or 2/3 x 12
• Using 12 counters,
0011 0010 1010 1101 0001 0100 1011
divide them into 3
groups. (Hint: the
denominator tells you how
many groups; the numerator
tells you how many to circle.)
• Circle 2 groups.
• How many
counters are
circled?
8
1
2
4
2/3 x 20= 8
Try this! Draw an array for the problem
on page 292.
XXXX
XXXX
XXXX
XXXX
0011 0010 1010 1101 0001 0100 1011
¾ x 16=
How many
groups should
you draw? 4
How many
counters did
you circle?
2
112
4
How many So, 12 of Susan’s stamps
groups shouldare from the United States
you circle? 3 and 4 stamps are not.
Share & Show
8 rows
0011 0010 1010 1101 0001 0100 1011
7/8 x 16= 14
How many rows of counters?
How many are in each row?
Circle ____ rows to solve.
How many counters are
circle?
2
7
14
1
2
4
Use a model to solve.
0011 0010 1010 1101 0001 0100 1011
2. 2/3 x 18=
3. 2/5 x 15=
4. 2/3 x 6=
1
2
4
Other methods to solve these problems:
0011 0010 1010 1101 0001 0100 1011
5. 5/8 x 24=
15
5
X 24 = 5 x 24= 120
• Multiplication:
8
8
The 8 slides over.
120 is an improper fraction:
8
divide to simplify.
15 x 8 = 120
1
2
4
15
8) 120
-120
0
Important!! Multiply the numerator by the
whole number.
Other methods to solve these problems:
0011 0010 1010 1101 0001 0100 1011
• Division, then
multiplication:
8 ÷8=1
1
3
5
x 24=
8
1. Look at the denominator
and the whole number. Is there
a number that will go into both
of them?
24÷8=3
15
1
2
Both numbers
(24 & 8) can be
divided by 8.
(Reduce by 8)
4
2. Now with 1 on the bottom, it is just 5 x 3= 15.