Transcript GCF and LCM

GCF and LCM
Greatest Common Factor
And
Least Common Multiple
Problem #1
• A discount store sells two
types of marbles. Blue
marbles come in bags of 18.
Red marbles come in bags of
30. I want to buy the same
number of each type of
marble.
LCM or GCF
• LCM
• How many of each type of marble
must I buy?
• How many bags of each type must I
buy?
• Predict how many of each type of
marble and how many bags you will
purchase.
LCM
• Use a factor tree
• Put prime numbers in order from least to
greatest (do not simplify to exponents)
•18 = 2
•30 = 2
3
3
3
5
Winners
•2 x 3 x 3 x 5 = 90
•90 is the LCM for
18 and 30
Back to Problem
• 90 marbles of each type must be
purchased
• Blue marbles, 18 per bag – need 5
bags
• Red marbles, 30 per bag – need 3
bags
• Check your prediction!
Problem #2
• You have a bag with 30 green
marbles and another bag with 42
yellow marbles. You want to
repackage the marbles into smaller
bags, and you want each bag to have
the same number of each type of
marble. You also want as many new
bags as you possibly can make.
LCM or GCF
• GCF
• How many of each marble will be in
the bags?
• How many bags will you be able to
make?
• Will you have any marbles left over?
GCF
• Use a factor tree
• Put prime numbers in order from least to
greatest (do not simplify to exponents)
•30 = 2
•42 = 2
3
3
5
7
Partners
•2 x 3 = 6
•6 is the GCF for
30 and 42
Back to Problem
• 6 marbles will go in each
bag
• 30 green marbles – 5 bags
• 42 yellow marbles – 7 bags
• No marbles left over!
Assignments
• In Class Assignment:
• Attachment D
GCF and
LCM
• Homework:
• Attachment C PB Puzzler