Grade 4, Module 2
Core Focus
• Reviewing addition and subtraction strategies and using them to make estimates
• Reviewing and extending use of the standard addition algorithm
• Reviewing time measurement; converting between minutes and hours;
introducing seconds
Addition and Subtraction
• Addition and subtraction skills learned in earlier grades are the basis for
understanding why the standard algorithm works. The standard algorithm
is the familiar paper-and-pencil procedure for adding multi-digit numbers that
most adults were taught in school.
• Strategies for adding and subtracting numbers mentally are important for real-life
situations. Students decompose (pull apart) and compose (put together) numbers
to make them more convenient to compute mentally.
2.1
Reviewing Addition Strategies
$325
How could you figure out the total
cost of these two items?
$59
Noah adjusted the two prices
and added 324 and 60.
384
How did Noah adjust the prices? Did it change the total cost?
Tyler used a different strategy to figure out the total cost.
What steps did he follow?
Using the Standard Algorithm for Addition
2.6
Any
Place)
What is (Regrouping
another way you in
could
figure
out the total cost?
300 + 0 = 300
20 + 50 = 70
5 + 9 = 14
300 + 70 + 14 = 384
What does this table show?
• Model for your child how you
think about estimating totals
when spending money at the
store or driving distances in
the car.
• Help your child practice
estimating answers before
calculating them exactly.
In real life, an estimate is
often all we need, so it is
important to become good at
estimating answers mentally.
• Ask your child to add the
whole numbers (no cents)
of large ticket items found
on, for example, car sale
circulars to practice using the
algorithm accurately.
+60
324
Ideas for Home
Drink Sales
In this lesson, students make mental strategies visible by using number
equations.
Week 1lines and
Week
2
Draw
on the number line to show how you would figure
How
outjumps
the total
Stepcould
Up you 1.figure
Juice
614
857
drinks sold in Weekout
1? the total. Then use words or numbers to show what you did.
Milk
531
435
standard
addition algorithm, what was called “carrying” is now called
a.
• In the
regrouping
numbers
are
into
new
place values in order
Gavinbecause
used
blocks
to represent
theregrouped
sales from each
type
of drink.
97
+ 68
=
He
then
moved
the
blocks
together
to
fi
gure
out
the
total.
to combine the quantities.
• Use place-value language
when talking about the
procedure: for 5,609 + 3,556
“9 ones plus 6 ones is
5 ones and 1 ten. 1 ten plus
0 tens plus 5 tens is 6 tens,
6 hundreds plus 5 hundreds is
11 hundreds or 1 hundred and
1 thousand, and 1 thousand,
plus 5 thousand, plus 3
thousand is 9 thousand.”
b.
Glossary
© ORIGO Education.
© ORIGO Education.
49 + 75 =
This group models 614 + 531, which is the same as 11 hundreds + 4 tens + 5 ones, which is
32
ORIGO Stepping Stones 4 • 2.1
totalTen
value
of the blocks?
do you or
know?
the What
sameisasthe
1,145.
hundreds
blocksHow
are traded
regrouped for 1 thousands block.
The 1 thousand, 1 hundred, 4 tens and 5 ones make a total of 1,145.
090115
What is another way to represent the same value?
I could trade 10 hundreds
Students decompose (pull
apart) and compose (put
together) numbers to make
them more convenient to
compute mentally.
1
Grade 4, Module 2
• Students round to solve addition and subtraction problems based on real-life
situations. They estimate purchase prices then calculate exact solutions using
composing and decomposing strategies.
Using the Standard Algorithm for Addition
(Composing Hundreds)
2.5
$249
How could you figure out the total cost
of these two items?
These numbers are difficult
to add mentally, so I would
use a written method to
calculate the total.
$475
Lilly used the standard addition algorithm to calculate the total.
1
1
4
What steps did she follow?
What does each small numeral above the 4 and 7 mean?
7
5
+ 2
4
9
7
2
4
What is another way to add these numbers?
steps
would you
to add
535 +(algorithms)
196?
In thisWhat
lesson,
students
usefollow
written
methods
to solve for exact totals.
What would you write?
Time
5
3
5
+ 1
9
6
• In earlier grades, students were introduced to reading and writing times to the
nearest minute before and past the hour, and to solving problems that involve
1. Estimate each total. Then use the standard addition algorithm
elapsedStep
timeUp
on analog
and digital
clocks.
to calculate
the exact
total.
• Students will
to include converting
between
a. extend their skills
b.
c.
d. minutes and hours,
Estimate
Estimate
Estimate
and seconds
and minutes.Estimate
8
6
+
3
6
7
+
8
3
4
8
+ 2
9
5
© ORIGO Education.
+ 2
Converting Between Units of Time
2.11
40 This table shows the length of time that activities took in one school
ORIGO Stepping Stones
day.
4 • 2.5
090115
© ORIGO Education.
Activity
Math
Time
1 hour
Reading
55 minutes
Writing
30 minutes
Library
30 minutes
Science
30 minutes
Art
25 minutes
Sport
45 minutes
Music
25 minutes
Social Studies
30 minutes
What was called “carrying”
is now regrouping because
numbers are regrouped into
new place values in order to
combine the quantities. E.g.
59 + 38 = 80 + 17 = 90 + 7 = 97.
H
T
O
4
2
8
+ 2
6
2
The standard addition
algorithm is the familiar
paper-and-pencil procedure
for adding multi-digit numbers
that most adults were taught
in school.
1
5
3 time
4 in hours,
4
8
3
7
3
• Work with elapsed
minutes
and2seconds.
Glossary
What is the total length of time for math and
science? How could you figure out the total
in minutes?
What is another way you could write the total?
1 hour + 30 minutes
is the same as
minutes
What are some other times in the
table that total more than one hour?
In the algorithm, the 17 is
regrouped into 1 ten and
7 ones; the 1 ten is regrouped
into the tens column.
Base-10 blocks are used to
model the regrouping and
recording process.
Ideas for Home
• Talk about time as often as
possible, e.g. say, “It’s 7:55.
We must leave for school at
8:30 — can you figure how
much time until then?” or
“The bus will come at 2:30.
See how my watch says
2:24? So how many more
minutes until the bus will
arrive?” Constant practice
is important for helping your
child learn to read, write,
and make sense of time.
1. Figure
outelapsed
the totaltime,
number
minutes.
In thisStep
lesson,
practice
andofconvert
between minutes and hours.
Upstudents
Then write the total another way.
a.
Rode to store
28 minutes
Shopped for DVDs 1 hour
b.
Watched TV
Read book
2 hours
58 minutes
2