Transcript Mixed Numbers

Mixed Numbers
Mixed numbers are whole
numbers and fractions together.
1
3 2
Subtracting Mixed Numbers
• To subtract mixed numbers, you must
make sure the fractions have the same
denominator, that’s the same bottom
number. Find the lowest common multiple
of the two denominators. That is the
number you will use for the denominator
in both fractions.
Shortcut for Finding the Least
Common Denominator or Least
Common Multiple
Check to see if the smaller denominator
divides evenly into the larger denominator.
If it does, use the larger denominator for
your LCD or LCM.
1
3 2
1
- 1 8
2 will divide evenly into 8,
so 8 is your LCD or LCM.
To Subtract Mixed Numbers
With Unlike Denominators
• Find the multiples of each
denominator.
1
3
4 = 4, 8, 12, 16, 20, 24
1
1
- 10 = 10, 20, 30, 40, 50
To Subtract Mixed Numbers
With Unlike Denominators
• Compare the lists of multiples.
Circle the common multiples
between the two lists.
1
3
4 = 4, 8, 12, 16, 20, 24
1
1
+ 10 = 10, 20, 30, 40, 50
To Subtract Mixed Numbers
With Unlike Denominators
Use the least common
multiple as the denominator.

1
3
4 = 4, 8, 12, 16, 20, 24
1
1
- 10 = 10, 20, 30, 40, 50
To Subtract Mixed Numbers
With Unlike Denominators
This number is also called
the least common denominator.

1
3
4 = 4, 8, 12, 16, 20, 24
1
1
- 10 = 10, 20, 30, 40, 50
To Subtract Mixed Numberss
With Unlike Denominators
• Find the equivalent fractions for 1/4
& 1/10 with 20 as the denominator.
1
3
4 x 5 =20
1
1
- 10
20
Ask yourself what
you multiply 4 by
to get 20.
To Subtract Mixed Numbers
With Unlike Denominators
• Find the equivalent fractions for 1/4
& 1/10 with 20 as the denominator.
1
x
5
=
3
4 x 5 =20
1
1
- 10
20
That’s right 5. Since
you are looking for
the equivalent fraction
you know the top
number must also be
multiplied by 5.
To Subtract Mixed Numberss
With Unlike Denominators
• Find the equivalent fractions for 1/4
& 1/10 with 20 as the denominator.
1
5
x
5
=
3
4 x 5 =20
1
1
- 10
20
To find the top number
just multiply 1 x 5 to
get your equivalent
fraction.
To Subtract Mixed Numbers
With Unlike Denominators
• Find the equivalent fractions for 1/4
& 1/10 with 20 as the denominator.
1
5
x
5
=
3
4 x 5 =20
1
1
- 10x 2 =20
Now ask what you
multiply the 10 by
to get 20.
To Subtract Mixed Numbers
With Unlike Denominators
• Find the equivalent fractions for 1/4
& 1/10 with 20 as the denominator.
1
5
x
5
=
3
4 x 5 =20
1
2
x
2
=
1
- 10x 2 =20
That’s right 2. Since yo
are looking for the
equivalent fraction you
know the top number
must also be multiplied
by 2.
To Subtract Mixed Numbers
With Unlike Denominators
• Now just subtract the
numerators.
1
5
x
5
=
3
4 x 5 =20
1x 2 = 2
- 1 10x 2 =20
3
20
Remember! We
never subtract the
denominators.
•
To Subtract Mixed Numbers
With Unlike Denominators
Now subtract the whole numbers.
1
5
x
5
=
3
4 x 5 =20
1x 2 = 2
- 1 10x 2 =20
3
2 20
Subtract These Mixed Numbers
1
10 3
1
- 3 6
6
6
Use the short
cut to find the
Least Common
Denominator
(LCD).
Subtract These Mixed Numbers
1
10 3 x 2 = 6
1
3
6 x 1 =6
Now find the
equivalent
fractions for
1/3 & 1/6.
Ask what do you multiply 3 by to get 6
and what do you multiply 6 by to get 6.
Subtract These Mixed Numbers
1
x
2
=
10
3x 2 = 6
1
x
1
=
- 3 6 x 1 =6
Since you are
writing equivalent
fractions, now
multiply the top
numbers by the
same number you
did in the
bottom.
Subtract These Mixed Numbers
1
2
x
2
=
10
3x 2 = 6
1
1
x
1
=
3
- 6x 1 =6
Now multiply
across.
Subtract These Mixed Numbers
1
2
x
2
=
10 3 x 2 = 6
1
1
x
1
=
3
- 6x 1 =6
1
6
Subtract your
new
numerators.
Subtract These Mixed Numbers
1
2
x
2
=
10 3 x 2 = 6
1
1
x
1
=
3
- 6x 1 =6
1
7
6
Subtract your
whole
numbers.
Subtract These Mixed Numbers
1
2
x
2
=
10 3 x 2 = 6
1
1
x
1
=
3
- 6x 1 =6
Your answer is:
1
7 6