Transcript Skip Count

Module 3
Lesson12, 13 & 14
Strategies for solving 9s
multiplication facts!
Skip Count
Skip Count by 6s to 60 …
612
18
24
30
36
42
48
54
60
Skip Count by 7s to 70 …
7
14
21
28
35
42
49
56
63
70
72
80
81
90
Skip Count by 8s to 80 …
8
16
24
32
40
48
56
64
Skip Count by 9s to 90 …
9
18
27
36
54
45
63
72
Multiply by 8 Pattern Sheet
2 minutes
End
Multiply by 8
6 x 8 = _______
Skip count up by 8s to solve!
8
16 24 32 40 48
Skip count down from 80 to check.
80 72 64 56 48
Now skip count up, but start at 5
40 48
6 x 8 = 48!
Multiply by 8
8 x 8 = _______
Skip count up by 8s to solve!
8
16 24 32 40 48 56
Skip count down from 80 to check.
80 72 64
Now skip count up, but start at 5
40 48 56 64
8 x 8 = 64!
64
Take from 10!
Say the following subtraction sentences in unit form:
18
20 – 2 (2 tens – 2 ones) = ______
30 – 3 = ________
27
40 – 4 = _____
36
50 – 5 = _____
45
60 – 6 = _____
54
70 – 7 = _____
63
72
80 – 8 = _____
90 – 9 = 81
_____
Problem of the Day
A scientist fills 5 test tubes with 9 mL of fresh water in each. She
fills another 3 test tubes with 9 mL of salt water in each. How
many mL of water does she use in all? Use the break apart and
distribute strategy to solve.
9
mL
9
mL
545
x9
72
3x9
27
The scientist has 72 mL of water in all.
Use the 9 = 10-1 strategy
to solve 9 x n facts
In the Problem of the day you solved 8 x 9.
Does 8 x 9 show:
8 groups of 9
9 groupsof 8
How does solving 8 x 9 help us solve 9 x 8?
That’s right!
The
tells
us the answer will be the same!
Use the 9 = 10-1 strategy
to solve 9 x n facts
Sometimes we can’t use the commutative property
because we don’t know either fact. Let’s use a 10s
fact to help solve a 9s fact we don’t know.
What’s easier to solve?
9x8
10 x 8
How many 8s are in 10 x 8?
10!
How many 8s are in 9 x 8?
9!
Use the 9 = 10-1 strategy
to solve 9 x n facts
Let’s look at it visually!
         
         
         
10 x 8
Use the 9 = 10-1 strategy
to solve 9 x n facts
Now let’s change the tape diagram to show 9 x 8:
         
         
         
Use the 9 = 10-1 strategy
to solve 9 x n facts
         
         
         
✗
9 x 8 = (10 x 8) – (1 x 8)
= (80) – (8)
Write a number sentence that shows the math we just did.
=72!!!
9x8
Practice That!
Sage and Ava read the same book. It takes Sage 8 minutes to
read a chapter, and Ava about 10 minutes. There are 9
chapters in the book. How many fewer minutes does Sage
spend reading than Ava?
9 90
x90
10 –
x8
72 =918
72
Sage reads 18 minutes less than Ava.
Identify Patterns in Multiples of 9
Lesson 13 Problem Set
A STORY OF UNITS
Name
1.
a.
3•3
Date
Skip-count by nine.
9
72
36
_______,
_______, _______, _______,
_______, _______, _______, _______,
_______, _______
When we skip
count
byplace
9s,in the
wecount-by.
are adding
9 each time.
b.
Look
at the tens
What is the pattern?
Adding by 9sc. can
tricky.
One
strategy
for adding by 9 is to add 10
Look atbe
the ones
place in the
count-by.
What is the pattern?
and then subtract one:
2.
Complete to make true statements.
a.
b.
c.
d.
10 more than 0 is _______,
10
f.
1 less is _______.
9
1 less is _______.
9
1 × 9 = _______
6 × 9 = _______
10 more than 9 is _______,
19
g.
10 more than 54 is _______,
1 less is _______.
18
1 less is _______.
2 × 9 = _______
7 × 9 = _______
10 more than 18 is _______,
h.
10 more than 63 is _______,
1 less is _______.
1 less is _______.
3 × 9 = _______
8 × 9 = _______
10 more than 27 is _______,
i.
9 × 9 = _______
4 × 9 = _______
10 more than 36 is _______,
1 less is _______.
5 × 9 = _______
10 more than 72 is _______,
1 less is _______.
1 less is _______.
e.
10 more than 45 is _______,
j.
10 more than 81 is _______,
1 less is _______.
10 × 9 = _______
Identify Patterns in Multiples of 9
Analyze the pattern in the product of the 9s multiplication problems:
18
2 x 9 = ______
27
3 x 9 = ________
4 x 9 = _____
36
5 x 9 = _____
45
6 x 9 = _____
54
7 x 9 = _____
63
8 x 9 = _____
72
81
9 x 9 = _____
What do you notice about the digits in the 10s and the 1s places?
Identify Patterns in Multiples of 9
Next, analyze each PRODUCT. How does the digit in the 10s place relate to the
number of groups?
18
2 x 9 = _____
27
3 x 9 = ________
36
4 x 9 = _____
45
5 x 9 = _____
54
6
x
9
=
_____
The digit in the
63
10s place is one
7
x
9
=
_____
LESS than the
72
number of
8 x 9 = _____
groups!
81
9 x 9 = _____
-1
Identify Patterns in Multiples of 9
Now, with a partner, add together the digits in each product. What pattern
do you notice?
18: 1 +8 = ?
2 x 9 = ___________
27
3 x 9 = ________
36
4 x 9 = _____
45
5 x 9 = _____
54
6
x
9
=
_____
Check your 9
63
facts by making
7
x
9
=
_____
sure the products
72
add up to 9!
8 x 9 = _____
81
9 x 9 = _____
9!
Identify Patterns in Multiples of 9
Do the patterns continue?
81
90
9 x 9 = _____
10 x 9 = ________
99
11 x 9 = ________
108
12 x 9 = ________
126
117
13 x 9 = _____
14 x 9 = ________
YES OR NO?
Fun math fact: For every 10 & 11 units digits in the tens place (or
above) will repeat … then the digits continue to count up. The units in the
ones place loop continuously through the digits 0 to 9.
How high does the pattern go??
Identify Patterns in Multiples of 9
You can also use your fingers to quickly solve 9s facts up to 10.
Put out your hands with all 10 fingers up.
Identify Patterns in Multiples of 9
Let’s solve the fact 3 x 9.
Put down the finger that matches the first factor.
The number of fingers to the left of the lowered finger are the 10s place.
How many fingers?
The number of fingers to the right of the lowered finger are the 1s place.
How many fingers?
Identify Patterns in Multiples of 9
Let’s solve the fact 7 x 9.
Identify Patterns in Multiples of 9
Let’s solve the fact 9 x 8.
Identify Patterns in Multiples of 9
Let’s solve the fact 9 x 4.
Problem Set