Factor Strings and
Prime Factorization
Everyday Math Lesson 1.9
Lesson Objectives
• I can tell the difference between
powers of ten written as ten
raised to an exponent .
• I can show powers of 10 using
whole number exponents
Mental Math
2x2=
5x6=
6*9=
2x3=
7*3=
8*9=
3x4=
7*6=
9*7=
4x5=
8x5=
8*6=
Let’s Check Your Homework!
• With a partner at your table,
compare your answers to your
study link 1.8. Resolve any
differences you may have. Be
ready to share your answers.
Math Message
8 + 8 and 4 * 4 are two names
for the number 16. In your
Math Work Journal write at
least 5 more names for the
number 16.
Vocabulary
• Add this vocabulary word to your
Vocabulary Chart:
– prime factorization
Introducing Factor Strings
• A factor string is a
multiplication expression that
has at least two factors that are
greater than one.
– Example: a factor string for the
number 24 would be 2 x 3 x 4
Your Turn
• Write another factor string for
the number 24; don’t use the same
numbers as the example we did
together.
Let’s Try Again!
• Make a factor string for the
number 7.
• What type of number is 7?
• You may not use 1 in factor
strings, and 7 has no other
factors except 7 and itself;
therefore it is a prime number.
Try this!
• Find factor strings for the
following numbers: 30, 50, 54, and
72.
Factor Rainbows
• The longest possible factor
string for a number is also known
as the prime factorization.
• In order to find prime
factorization we can also use a
factor tree.
On Your Own!
• Try finding the prime
factorization of the following
numbers using factor trees: 36,
18, and 9.
Finding Factor Strings and
Prime Factorization
• With your assigned partner,
complete Student Journal Pages
25 and 26.
• You will have 20 minutes to
complete this assignment, when
you hear the bell, return to your
seat and be ready to share your
answers.
Let’s Play “Name That
Number”!
• Turn to page 325 in your SRB and
read about how to play “Name
That Number”.
• With your assigned partner, you
will have 15 minutes to play. 