ACTIVITY
WORKBOOK 4:1
PAGE 91-94
Use play money to trade the following amounts for the least number of coins.
a) 7 quarters
b) 9 quarters
c) 7 nickels
d) 12 dimes
e) 7 dimes and 1 nickel
Extension
Repeat the weighing activity at the end of the lesson with the actual weights of the coins:
Nickel: 3.95 grams, Dime: 1.75 grams, Quarter: 4.4 grams, Loonie: 7 g
Literature Connection
Smart by Shel Silverstein, contained in Where the Sidewalk Ends.
Read this poem to your class. With each stanza, stop and ask the students how much money
the boy in the story has. Give students play money to use as manipulatives so they can each
have the same amount of coins as described in the poem.
This is an excellent demonstration that having more coins does not necessarily mean having
more money.
NS4-50
Making Change Using Mental Math
Pose a sample problem. You would like to buy a pen which costs 18¢, but
you only have a quarter to pay with. How much change should you get back?
GOALS
Students will make change
for amounts less than $1
using mental math.
PRIOR KNOWLEDGE
REQUIRED
Counting by 1s and 10s
Subtraction
VOCABULARY
skip counting
penny
nickel
dime
quarter
90
loonie
cent
dollar
change
Rather than starting with a complicated subtraction question that includes
decimals and carrying, show students how to ‘count up’ to make change.
Demonstrate that you can first count up by 1s to the amount. In this case
you would start at 18 and count up: 19, 20, 21, 22, 23, 24, 25. You would
need 7¢ as change. Review the finger counting technique, keeping track of
the number counted on their fingers.
Model more examples, getting increasingly more volunteer help from the
class as you go along.
Have students practice this skill with play money, if helpful. They
should complete several problems of this kind before moving on.
Some sample problems:
a) Price of an orange = 39¢
b) Price of a hairband = 69¢
c) Price of a sticker = 26¢
Amount paid = 50¢
Amount paid = 75¢
Amount Paid = 30¢
Pose another problem: You would like to buy a flower that costs $80¢, but
you only have a loonie to pay with. How much change should you get back?
Before the students start to count by 1s to 100, tell them that you will show
them a faster way to do this.
TEACHER’S GUIDE
WORKBOOK 4:1
PAGE 93-94
Explain that instead of counting up by 1s, you can count by 10s to 100. Starting at 80 you would
count up: 90, 100 to $1.
Give students several problems to practice. Some sample problems:
a) Price of a newspaper = 50¢
b) Price of a milk carton = 80¢
c) Price of a paper clip = 10¢
Amount Paid = $1.00
Amount Paid = $1.00
Amount Paid = $1.00
Pose another problem: You would like to buy a postcard that costs 55 cents, but you only have a
loonie to pay with. How much change should you get back?
Explain that you can count up by 1s to the nearest 10, then you can count by 10s to $1 (or the
amount of money paid). In this case you would start at 55 and count up to 60: 56, 57, 58, 59, 60.
Then count up by 10s. Starting at 60 you would count up: 70, 80, 90, 100. At the end, you will have
counted five ones and four 10s, so the change is 45¢.
Demonstrate the above problem using the finger counting technique. Explain to the students that
this can be clumsy, because it is easy to forget how many 1s or how many 10s you counted by.
How could you use this method to solve the problem without the risk of forgetting?
Model another example. You would like to buy a candy bar costs 67¢, but you only have a loonie
to pay with.
STEP 1: Count up by 1s to the nearest multiple of 10 (Count 68, 69, 70 on fingers).
STEP 2: Write in the number that you have moved forward and also the number that you
are now ‘at’ (Write “counted 3, got to 70¢”).
STEP 3: Count up by 10s to $1.00. Write in the number that you have counted up.
(Count 80, 90, 100, write 30¢)
STEP 4: Add the differences to find out how much change is owing (3¢ + 30¢ = 33¢).
Let a couple of volunteers model this method with sample problems. Give the students another
several problems to complete in their notebooks, such as:
a) Price of a bowl of soup = 83¢
b) Price of a stamp = 52¢
c) Price of a pop drink = 87¢
d) Price of an eraser = 45¢
e) Price of a candy = 9¢
Amount Paid = $1.00
Amount Paid = $1.00
Amount Paid = $1.00
Amount Paid = $1.00
Amount Paid = $1.00
Assessment
a) Price of a pencil = 77¢
b) Price of a chocolate bar = 62¢
c) Price of a candy = 17¢
Amount Paid = $1.00
Amount Paid = $1.00
Amount Paid = $1.00
Bonus
a) Price of an action figure = $9.99
b) Price of a book = $4.50
WORKBOOK 4
Part 1
Number Sense
Amount Paid = $10.00
Amount Paid = $5.00
91
WORKBOOK 4:1
PAGE 93-94
Play Shop Keeper
ACTIVITY
Set up the classroom like a store, with items set out and their prices clearly marked. The prices
should be under $1.00.
Tell the students that they will all take turns being the cashiers and the shoppers. Explain that making
change (and checking you’ve got the right change!) is one of the most common uses of math that
they will encounter in life!
Allow the students to explore the store and select items to ‘buy’. Give the shoppers play money to
‘spend’ and give the cashiers play money to make change with. Ask the shoppers to calculate the
change in their heads at the same time as the cashiers when paying for the item. This way, students
can double check and help each other out. Reaffirm that everyone needs to work together, and
should encourage the success of all of their peers.
Allow the students a good amount of time in the store. Plan at least 30 minutes for this exploration.
Extensions
1. Once students have calculated the change for any question, have them figure out the least
number of coins that could be used to make that change.
2. This would be a great lead up to an actual sale event. If your community or school has an
initiative that your class wanted to support, you could plan a bake sale, garage sale, etc.
that would raise funds for the cause. Students would find the pretend task even more
engaging if it was a ‘dress rehearsal’ for a real event.
92
TEACHER’S GUIDE
NS4-50: Making Change Using Mental Math
page 93
1. Calculate the change owing for each purchase.
a) Price of a pencil = 42¢
Amount Paid = 50¢
b) Price of an eraser = 34¢
Amount paid = 50¢
Change = ________
d) Price of a ruler = 56¢
Amount Paid = 60¢
c) Price of a sharpener = 81¢
Amount paid = 90¢
Change = ________
e) Price of a marker = 78¢
Amount Paid = 80¢
Change = ________
Change = ________
f)
Change = ________
Price of a notebook = 63¢
Amount Paid = 70¢
Change = ________
2. Count up by 10s to find the change owing from a dollar (100¢).
Price Paid
Change
Price Paid
Change
Price Paid
a) 90¢
d) 40¢
g) 20¢
b) 70¢
e) 10¢
h) 60¢
c) 50¢
f)
i)
30¢
Change
80¢
3. Find the change owing for each purchase.
HINT: Count up by 10s.
a) Price of a lollipop = 50¢
Amount Paid = $1.00
b) Price of an eraser = 60¢
Amount paid = $1.00
Change = ________
Change = ________
d) Price of a banana = 60¢
Amount Paid = $1.00
Change = ________
g) Price of a gumball = 10¢
Amount Paid = $1.00
Change = ________
e) Price of a patty = 80¢
Amount Paid = $1.00
c) Price of an apple = 30¢
Amount paid = $1.00
Change = ________
f)
Change = ________
h) Price of a juice = 40¢
Amount Paid = $1.00
Change = ________
Price of a pencil = 20¢
Amount Paid = $1.00
Change = ________
i)
Price of a popsicle = 70¢
Amount Paid = $1.00
Change = ________
4. Find the smallest 2-digit number ending in zero (i.e. 10, 20, 30, 40...) that is greater than the number
given.
a) 72
80
b) 54
c) 47
d) 26
e) 58
f)
7
Number Sense 1
NS4-50: Making Change Using Mental Math (continued)
page 94
5. Make change from $1.00 for the numbers written below. Follow the steps shown for 17¢.
Step 1:
Find the smallest multiple of 10 greater than 17¢.
17¢
Step 2:
Find the differences.
20 – 17 and 100 – 20
17¢
Step 3:
Add the differences.
3¢ + 80¢
20¢
3
20¢
80
100¢
Change = 83¢
b)
a)
68¢
100¢
100¢
72¢
Change = __________
Change = __________
c)
d)
53¢
100¢
100¢
23¢
Change = __________
Change = __________
e)
f)
48¢
100¢
84¢
100¢
Change = __________
Change = __________
6. Find change from 100¢ for the following. Try to do the work in your head.
a) 58¢ _______
b) 64¢ _______
c) 27¢ _______
d) 36¢ _______
e) 52¢ _______
f)
g) 97¢ _______
h) 14¢ _______
i)
j)
29¢ _______
89¢ _______
91¢ _______
BONUS
7. Find the change for the following amount in your head.
a) Price: 37¢
Amount Paid: 50¢
Change Required: _________
b) Price: 58¢
Amount Paid: 75¢
Change Required: ______
Number Sense 1