Divide and Conquer

1
Divide and Conquer

• All About Division

Sharing
Repeated Subtraction
Stories
2
What is division?

• Division is the inverse, or opposite, of
  multiplication.

just as
subtraction
division
is the opposite of..
is the opposite of..
addition
multiplication

• Division is an operation that tells how many
  groups there are and how many are in each group.

3
What does division look like?
24 6 4
A division problem can be written horizontally
using the division symbol.
24 6
A division problem can be written as a fraction.
A division problem can be written in a division
box.
4
Lets learn the Division Lingo!
24 6 4
dividend the number being divided (total number
of items)
divisor the number by which another number is
divided ( of groups)
quotient- the answer to a division problem ( of
items in each group)
5
dividend
24 is the
6 is the
divisor
4 is the
quotient
6
Draw a fat bridge map in your notebook.
Remember Bridge maps help us see relationships!
just as
product
quotient
is the answer in..
is the answer in..
multiplication
division
How is product related to multiplication?
7
Fact Families

• A fact family can show how multiplication and
  division are related.
• Remember that fact families are groups of number
  sentences that use the same numbers.

Here is a fact family for 7, 3, and 21.
7 x 3 21
21 3 7
3 x 7 21
21 7 3
8
Write fact families for..
4, 2, 8
3, 9, 27
5, 3, 15
9
Division as Sharing

• We use division when we want to divide a number
  into equal groups.

Anndel, Austin, and Toni have 12 toy cars to
share equally. How many will each get?
To decide, think of putting the 12 cars into 3
equal groups. You can draw a picture to help you.
10
When all the cars are grouped, there will be 4 in
each group.
You can also use division to find the number in
each group.
The following division number sentence describes
the situation.
12 3 4
Total number, or dividend
number in each group, or quotient
Number of equal groups, or divisor
11
Lets explore division as sharing!

• Remember that when we divide, we share equally!

There are 9 flowers. Christa must divide the
flowers equally into 3 vases. How many flowers
will be put into each vase?
9 3 3
Each vase will have 3 flowers.
12
Lets solve some more Problems!

• Solve the problems on your dry erase board by
• drawing a picture
• writing a division number sentence
• labeling your answer

Lets show our division smarts!
13
Lydia has 12 tennis balls. She must put them in 4
canisters. How many tennis balls must she put in
each canister?
Remember Dividing means sharing equally!
14
One box contains 12 granola bars. Two bars are in
each package. How many packages are in each box
of granola bars?
Remember Dividing means sharing equally!
15
There are 16 bananas and 4 bunches. How many
bananas are in each bunch?
Remember Dividing means sharing equally!
16
Division as Repeated Subtraction

• Multiplication is the same thing as repeated
  addition.
• Addition is the inverse of subtraction and
  division is the inverse of multiplication so

just as
multiplication
division
is the same as..
is the same as..
repeated addition
repeated subtraction
17
Lets explore division as repeated subtraction!

• Justin has 12 plants to put into clay pots. He
  wants to put 2 plants in each pot. How many clay
  pots does he need?

Lets use repeated subtraction to find
out how many groups of 2 are in 12.
Start with 12 plants and subtract 2 at a time
until there are no plants left. Then count the
subtractions.
12 - 2 10
We can subtract 2 from 12 6 times. There are 6
groups of 2 in 12.
10 -2 8
8 - 2 6
6 -2 4
4 - 2 2
12 2 6
2 - 2 0
18
Lets use repeated subtraction!

• This is another strategy that we can use to help
  us solve division problems!

DeAndre has 15 sweaters. He is packing them into
boxes. Each box holds 3 sweaters. How many boxes
does DeAndre need?
15 3 12
We can subtract 3 from 15 5 times. There are 5
groups of 3 in 15.
Start with 15 plants and subtract 3 at a time
until there are no sweaters left. Then count the
subtractions.
12 - 3 9
9 - 3 6
6 - 3 3
3 - 3 0
15 3 5
19
Lets solve some more Problems!

• Solve the problems on your dry erase board by
• using repeated subtraction
• writing a division number sentence
• labeling your answer

Lets show our division smarts!
20
Damien has 35 stickers. He wants to put 5
stickers on each sheet in his book. How many
sheets will he need?
How many groups of 5 are in 35?
21
Raymond has 18 buttons. He wants to put 6 buttons
in each container. How many containers will he
need?
How many groups of6 are in 18?
22
Kolby has to carry 24 boxes to her room. She can
carry 3 boxes on each trip. How many trips will
she take?
How many groups of 3 are in 24?
23
We have learned different division strategies!

• We can solve problems by thinking of division as
• dividing a number into equal groups
• sharing equally
• repeated subtraction

24
The Doorbell Rang

• Lets share cookies!
• We are going to use our counters as cookies.
• Listen carefully to the story!
• As I read aloud, we will act out the division
  situations using our counters.
• We will also write division number sentences to
  match these situations.

25
What is the main idea of a division story?

• Mr. Chan asked his third-grade students to
• write division stories for the number sentence
• 18 3 n.

Mona decided to write a story about the goldfish
in their classroom.
I have 18 goldfish and want to put 3 in each fish
bowl. How many fish bowls will I need?
Pick a strategy and solve this problem in your
math notebook! ?
26
How can you write a division story?
Use the picture to help you!
24 juice boxes
24 4 n
27
How can you write a division story?
Use the picture to help you!
30 5 n