Grade 2, Module 12
Core Focus
• Using various strategies to subtract (up to three-digit numbers)
• Introducing and working with cups, pints, quarts, and liters
Subtraction
• It is important that students have extended experience in decomposing (pulling
apart) numbers (e.g. 342 can be split into 3 hundreds, 4 tens, and 2 ones, or
2 hundreds, 14 tens, and 2 ones, and so on).
• Thinking about regrouping 1 hundred for 10 tens, or 1 ten for 10 ones is important
background experience for subtraction with numbers that require regrouping.
12.1
Decomposing Three-Digit Numbers
Look at this block picture.
What number does it show?
What could you do with the blocks to make 14 ones blocks
and keep the total same?
I could trade 1 tens block for 10 ones blocks.
That makes 14 ones blocks and the total does not change.
In this lesson, students work with regrouping numbers where
Look at this block picture.
a ten
or a hundred has to be decomposed.
What number does it show?
How many hundreds blocks would you have left?
Subtracting
One-Digit
Numbers
How many
ones blocks would
there be?
12.2
Does the (with
total change?
Bridging)
from Three-Digit Numbers
272
121214
© ORIGO Education.
• One strategy students use is counting back jump by jump on a number line.
They use their knowledge of basic facts to jump back to friendly numbers, usually
could you do with the blocks to make 13 tens blocks
multiples of ten or aWhat
hundred.
and keep the total same?
ORIGO Stepping Stones 2 • 12.1
Look at this picture of blocks.
What number does it show?
How would you change the blocks so that
you could take away 5 ones blocks?
I need more ones so I
could trade a tens block
for 10 ones blocks.
Then it is easy to take
away the 5 ones.
163 Ð 5 = 158.
© ORIGO Education.
158
150
3
160
163
170
I could use a number line and jump
back 3 to 160 then 2 more to 158.
Step Up
• To reinforce the idea of
decomposing numbers,
talk with your child about
other experiences they
have had with this concept.
With money, ten dimes or
a one dollar bill both equal
$1.00, while 10 can be one
dime or ten pennies. With
time, children know that 1
hour is also 60 minutes. To
solve real-life problems, we
sometimes need to change
the units. To calculate the
minutes left in one hour after
15 minutes have passed,
we change one hour to
60 minutes to subtract
the 15 minutes and see that
45 minutes remain.
• Ask your child to describe
their favorite strategy for
subtracting two- and
three-digit numbers from
three-digit numbers. Follow
up by using their strategy
to solve subtraction
problems yourself.
Glossary
Students decompose
numbers by place value –
hundreds, tens, and ones.
How would you figure out 163 − 5?
2
Ideas for Home
1. Use blocks to help you subtract. Then write the difference.
In this lesson, students are encouraged to use a range of
strategies to subtract one-digit numbers from three-digit numbers.
a. 1 51 − 4 =
b. 276 − 8 =
c. 474 − 6 =
d. 345 − 8 =
e. 168 − 9 =
f. 593 − 5 =
a.
265 is the same as
1 hundred,
16 tens, and 5
ones
1
Grade 2, Module 12
• For students to solve problems such as 236 − 80, the 2 hundreds will need to be
regrouped to 1 hundred and 10 tens to enable thinking that involves subtracting the
parts (e.g. 13 tens − 8 tens is 5 tens so 236 − 80 = 156).
• Students focus on very different subtraction strategies — “counting back” or
“counting on” and “using place value.” Using a number board or number line
is encouraged for counting back or counting on, and tens and ones blocks are
encouraged for using place value (subtracting hundreds, tens, and ones separately).
• The strategies in this module lead to the development of the written procedures
for addition and subtraction in later years.
12.4
Using Place Value to Subtract Two-Digit Numbers from
Three-Digit Numbers (with Bridging)
• Breaking single-digit numbers
into two parts is a key skill
for counting on or counting
back on a number line. Ask
your child to find all the
combinations to make each of
the 2 − 9 (e.g. 8 can be broken
into 7 and 1, 6 and 2, etc.).
I would use blocks to show 216. I would have to trade 1
hundreds block for 10 tens blocks. Then it's easy to figure out.
I would use a number line to subtract like this.
2
184
180
10
186
10
196
190
200
10
206
216
210
220
How would you figure out 253 – 26 using blocks?
In this
are
encouraged
to use place-value
Howlesson,
would youstudents
figure out 253
– 26
using a number line?
strategies to subtract two-digit numbers from three-digit numbers.
Step Up
1. Use blocks to help you subtract. Then write the difference.
Customary Measurement: Capacity
a. 245 − 38 =
b. 157 − 29 =
c. 584 − 36 =
© ORIGO Education.
• Students learn about standard units to measure capacity — cups, pints, quarts, and
d. 423 − 32 =
e. 213 − 21 =
f. 426 − 34 =
liters. Students use the measures to compare how much various containers hold.
278
121214
12.9
ORIGO Stepping Stones 2 • 12.4
Introducing Cups, Pints, and Quarts
All of these containers can be called cups.
• Play this subtraction game with
your child using a number line.
Start at 350. Roll two dice to
create a two-digit number and
subtract it from 350. Take turns
rolling the dice and subtracting
the two-digit numbers from the
running total. After 5 rounds,
the winner is the person who is
closest to zero.
Glossary
1 pint = 2 cups
If a recipe told you to use a cup of flour, which container would you use? Why?
Would it make any difference? How do you know?
In recipes, the word cup is a unit of measure. Even though all cup measures hold the
same amount, they can be different shapes.
Where have you seen or heard
the words pint and quart?
1 quart = 4 cups
1 liter is a little more than
1 quart
Cups, pints, and quarts
are units of capacity.
Capacity means how much a
container can hold. So one pint
of milk is the amount of milk
that can fit in a one-pint bottle.
1 pint
1. Write more or less to show whether these containers would hold
Steplesson,
Up
In this
students
are
more than or
lessintroduced
than one cup. to the standard customary
units — cups, pints, and
quarts
— and
use them toc. measure the
a.
b.
capacity of containers.
Cups, pints, and quarts
are units of capacity.
Capacity means how much a
container can hold. So one pint
of milk is the amount of milk
2
TOMATOES
1 kg
.
© ORIGO Education.
• Encourage your child to help
you in the kitchen, including
measuring food or drink
using cups, pints, or quarts.
Simple tasks like preparing
lemonade or measuring rice
(and water for cooking it) can
be excellent activities to work
with measuring.
• At the grocery store, ask your
child to find items that are
labeled with pints, quarts, or
liters to help them become
familiar with the different sizes.
$32
Shona has $216 in her savings.
If she buys this skateboard, how much money will she have left?
How could you figure it out?
Ideas for Home