Transcript x 13

5 Minute Check
Complete in your notebook.
1.
2.
3.
9
3
10 + 5
7
2
3
9
7
8
-3
1
7
-2
5
6
5 Minute Check
Complete in your notebook.
1.
9
3
10 + 5
5 Minute Check
Complete in your notebook.
1.
9
10
3
5
+ =
9
10
6
10
+ =
15
10
=1
1
2
5 Minute Check
Complete in your notebook.
2.
7
2
3
-3
1
7
5 Minute Check
Complete in your notebook.
2.
7
2
3
-3 = 1
7
23
3
161
21 -
7 x 23
7 x 3
22
7
22 x 3
7 x 3
66
21
=
95
21
=4
11
21
5 Minute Check
Complete in your notebook.
3.
9
7
8
-
2
5
6
5 Minute Check
Complete in your notebook.
3.
9
7
8
-
2
5
6
=
79
8
3 x 79
3 x 8
237
24
-
17
6
-
17 x 4
6 x 4
-
68
24
=
169
24
1
24
=7
Monday, Oct 21
Lesson 4.1
Estimate Products of Fractions
Estimate Products of Fractions
Objective: To understand how to estimate
the product of fractions and /or whole
numbers.
Estimate Products of Fractions
At the end of this lesson you should be able
to answer the following question.
Why is estimating products useful?
Estimate Products of Fractions
To multiply fractions, multiply the numerators
and multiply the denominators, then simplify if
needed.
Example x
=
3
2
6
4
5
20
x
=
x
=
=
3
10
Estimate Products of Fractions
To multiply a fraction and whole number,
convert the whole number to a fraction, then
multiply as before.
Example 2
5
x 14
2
5
x
x
x
14
1
=
28
5
3
5
= =5
=
Estimate Products of Fractions
There are three methods to use to
estimate. Each method is used in a
specific situation.
Method 1 – Estimating the product of a
fraction and whole number.
Method 2 – Estimating the product of
two fractions.
Method 3 – Estimating the product of
two mixed numbers.
Estimate Products of Fractions
1. When estimating the product of a
fraction and whole number use a
comparable number for the whole number
or the denominator (whichever is larger).
The comparable number should be
divisible by the smaller number.
Estimate Products of Fractions
Estimate:
1
4
x 13
Estimate Products of Fractions
Estimate:
1
4
x 13
Which number is larger?
Estimate Products of Fractions
Estimate:
1
4
x 13
What number is close to 13,
but divisible by 4?
Estimate Products of Fractions
Estimate:
1
4
x 13
1
4
x 12
Estimate Products of Fractions
Estimate:
1
4
x 13 ≈ 3
1
4
12
1
x =
12
4
=3
Estimate Products of Fractions
Estimate
1
4
x 13 ≈ 3
We can also make a model.
3
3
12
3
3
Estimate Products of Fractions
Estimate:
1
7
x3
Estimate Products of Fractions
Estimate:
1
7
x3
Which number is larger?
Estimate Products of Fractions
Estimate:
1
7
x3
What number is close to 7,
but divisible by 3?
Estimate Products of Fractions
Estimate:
1
1
7
2
x 3≈
1
6
x
3
1
3
6
= =
1
2
Estimate Products of Fractions
Estimate
5
6
x 13
(Do this on your own)
Estimate Products of Fractions
Estimate
5
6
5
6
x 13 ≈ 10
x =
12
1
2 2
12
2 2
60
6
2
= 10
2
Estimate Products of Fractions
2
Estimate 5
11
x
(Do this on your own)
Estimate Products of Fractions
2
Estimate 5
11≈ 4
x
2
5
10
1
x =
20
5
=4
Estimate Products of Fractions
2. When multiplying a fraction by a fraction, an
estimate can be determined by rounding the
fractions.
Estimate Products of Fractions
2. When multiplying a fraction by a fraction, an
estimate can be determined by rounding the
fractions.
 Round up to 1 when the numerator is
almost as large as the denominator.
Example: 7/8 rounds up to 1
Estimate Products of Fractions
2. When multiplying a fraction by a fraction, an
estimate can be determined by rounding the
fractions.
 Round up to 1 when the numerator is
almost as large as the denominator.
 Round to ½ when the numerator is about half
the denominator.
Example: 3/7 rounds to 1/2
Estimate Products of Fractions
2. When multiplying a fraction by a fraction, an
estimate can be determined by rounding the
fractions.
 Round up to 1 when the numerator is
almost as large as the denominator.
 Round to ½ when the numerator is about half
the denominator.
 Round down to zero when the numerator is
much smaller than the denominator.
Example: 1/5 rounds to 0
Estimate Products of Fractions
Can either be estimated up or down
0
¼
½
¾
1
Estimate Products of Fractions
Round the fraction.
3
5
Estimate Products of Fractions
Round the fraction.
3
5
≈
1
2
Since 3 is about half of 5, we round to ½.
Estimate Products of Fractions
Round the fraction.
1
9
Estimate Products of Fractions
Round the fraction.
1
9
≈0
Since 1 is much less than 9, we round to 0.
Estimate Products of Fractions
Round the fraction.
9
10
Estimate Products of Fractions
Round the fraction.
9
10
≈1
Since 9 is close to 10, we round to 1.
Estimate Products of Fractions
Estimate.
1
3
x
7
9
Round each fraction, then perform the
operation.
Estimate Products of Fractions
Estimate.
1
3
1
2
x
7
9
x 1=
1
2
Estimate Products of Fractions
Estimate.
1
9
x
4
5
Estimate Products of Fractions
Estimate.
1
9
x
4
5
0 x 1= 0
Estimate Products of Fractions
3. When estimating the product of two mixed
numbers, round the mixed number to the
nearest whole number.
For example:
6
1
7
4
2 x3
3 x 3= 9
Estimate Products of Fractions
Estimate:
1
5
8
6
3 x1
Estimate Products of Fractions
Estimate:
1
5
8
6
3 x1
3 x 2=6
Estimate Products of Fractions
Recap –
When estimating a product of a fraction and
whole number, choose a comparable number
for the whole number or the denominator of
the fraction (which ever is larger) which are in
the same multiples list.
Estimate Products of Fractions
Recap –
When estimating a product of two fractions
round the fractions to 0, ½ or 1.
Estimate Products of Fractions
Recap –
When estimating a mixed number round to the
nearest whole number.
Estimate Products of Fractions
Why is estimating products useful?
Estimate Products of Fractions
Friday is the last day to turn in
any missing assignments.
Estimate Products of Fractions
Agenda Notes
Homework –
Homework Practice 4-1
Due Tuesday, Oct 22
Mid Chapter 4 Quiz –Monday, Oct 28