Name:___________________________________
Period:_______________
Finding
a
Common
Denominator
Finding
a
common
denominator
one
of
the
most
important
fraction
concepts
to
know.
You
need
to
fin
a
common
denominator
in
order
to
compare,
add,
and
subtract
2
pairs
of
fractions.
2
3
Example:
Let’s
find
the
common
denominator
for
these
pairs
of
fractions,
and .
3
5
In
order
to
find
the
common
denominator,
we
need
to
find
some
multiples
of
each
denominator:
€
Some
multiples
of
3
are:
3,
6,
9,
12,
15,
18
Some
multiples
of
5
are:
5,
10,
15,
20,
25,
30
What
multiple
do
they
both
have
in
common?
The
common
multiple
is
15.
Then,
we
use
15
as
a
common
denominator
to
make
the
fractions
equivalent.
15 ÷ 3 = 5
15 ÷ 5 = 3
2 2 × 5 10 3 3 × 3 9 =
=
=
=
3 3 × 5 15
5 5 × 3 15
10 9
2 3
≥ ,so ≥ 15 15
3 5
€
€
Finding
which
fraction
is
larger
would
be
very
hard
if
we
did
not
find
a
common
denominator.
€
Directions:
Find
a
common
denominator
for
each
pair
of
fractions,
and
then
make
both
fractions
equivalent.
1
4
1.
and 2
7
€
Common
Denominator_________________
The
new
fractions_____________________________
8
7
2.
and 9
8
€
Common
Denominator_________________
The
new
fractions_____________________________
Name:___________________________________
Period:_______________
1
1
3.
and 6
8
€
Common
Denominator_________________
The
new
fractions_____________________________
Directions:
Use
common
denominators
to
find
which
fraction
is
greater.
Circle
the
fraction
that
is
greater.
5
6
4.
and 9
10
€
2
21
5.
and 3
30
€
3
5
6. and 8
11
€
Directions:
Use
common
denominators
to
find
which
fraction
is
smaller.
Circle
the
fraction
that
is
smaller.
2
5
7.
and 3
6
€
8
23
8.
and 9
27
€
3
3
9.
and 7
6
€