Unit 4 – GCF and LCM
Greatest Common Factor
Least Common Multiple
 Objective: As a result in learning, students should be able to
distinguish between prime and composite numbers and list the
factors of a given number.
Warm Up:
Which number is prime?
9
61
102
363
• What is the difference between a prime
and a composite number?
• What is a factor?
• What strategies can you use to find the
factors of a number?
• Take WWAK
• Use Making Rectangles handout
• HW: Prime and Composite Coloring
handout
composite A number with more
number
than two factors.
factor
prime
number
A number multiplied by
another number to get a
product.
A number with exactly two
factors, 1 and itself.
 Objective: As a result in learning, students should be able to
distinguish between prime and composite numbers and list the
factors of a given number.
Warm up:
Find all the factors of
28. Circle the prime
numbers
.
• Factors and prime
factorization Check-up
Handout
• Play the factor game (49)
• HW:
 Objective: As a result in learning, students should be able to find
the greatest common factor of two numbers
Warm Up:
What does
“greatest common
factor” mean?
greatest
common
factor
The largest common
factor of two or more
given numbers.
• GCF notes
• Finding GCF
• HW: Most Wanted Poster
 Objective: As a result in learning, students should be able to find
the greatest common factor of two numbers.
Warm Up:
Your table has two pieces of string
that you need to cut. One piece of
string is 36 inches and the other is
80 inches. Cut all the string into
pieces of equal lengths. What is the
greatest possible length of each
piece?
Angie works in a pet store. She needs
to divide 36 angelfish, 42 rainbow fish,
and 126 goldfish into aquariums so that
each aquarium has the same number of
each type of fish, and there are no fish
left over. What is the greatest number
of aquariums Angie can fill under these
conditions?
There are 12 boys and 18 girls in Mr.
Ruiz's science class. The students must
form lab groups. Each group must
have the same number of boys and
the same number of girls. What is the
greatest number of groups Mr. Ruiz
can make if every student must be in a
group?
Ms. Spain and Mr. France have donated a
total of 90 hot dogs and 72 bags of chips for
the class picnic. Each student will receive
the same amount of refreshments. All
refreshments must be used.
• What is the greatest number of students
that can attend the picnic?
• How many bags of chips will each student
receive?
• How many hotdogs will each student
receive?
The elementary school lunch
menu repeats every 20 days;
the middle school lunch menu
repeats every 15 days. Both
schools are serving pizza today.
In how many days will both
schools serve pizza again?
Ultimate Challenge Problems
 Objective: As a result in learning, students should be able to find
the least common multiple of two numbers.
Warm Up:
Markers are sold in packs of 6. Pens
are sold in packs of 2. There are 30
students in the class. What is the
least number of packs the teacher
should buy so that each student has
a marker and a pen with none left
over?
least
common
multiple
The smallest number,
other than zero, that
is a multiple of two or
more given numbers.
• What is a multiple?
• How can you determine the multiples two numbers have in
common?
• As a review of multiples, the students will do a quick activity called
"Hundred Chart Multiples."
• Place a basket of Unifix cubes at each group of students.
• Give each student a hundreds chart.
• Begin with two numbers such as 2 and 6.
• Students use one color cube to cover all the multiples of 2 up to
50.
• Students use another color cube to cover all the multiples of 6 up
to 50.
• Lead the students in a discussion of how the common multiples of
2 and 6 are the numbers with two cubes on them.
• Students will then be able to identify the least common multiple.
(the least common multiple of 2 and 6 is 12)
• Clear the boards and repeat the process using other numbers.
Methods to finding LCM handout
HW:
 Objective: As a result in learning, students should be able to solve
problems involving GCF and LCM.
Warm Up:
What is the LCM of
12 and 8?
Two students are building
blocks. Reece's blocks are 4
cm high, and Maddy's
blocks are 9 cm high. How
tall will their stacks be when
they are the same height
for the first time?
Pam is making fruit baskets. She
has 30 apples, 24 bananas, and
12 oranges. What is the greatest
number of baskets she can make
if each type of fruit is distributed
equally among the baskets?
LCM Practice
Riddle Me This
Objective: As a result in learning, students should be
able to solve problems involving GCF and LCM.
Classifying Numbers
Product Game
Objective: As a result in learning, students should be
able to solve problems involving GCF and LCM.
 Word Problem Challenge
 Around the World
 Exit Ticket