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© Pearson Education, Inc., publishing as Pearson Prentice Hall.
Class
Date
Name
Adding and Subtracting Decimals
Lesson 1-7
NAEP 2005 Strand: Number Properties and Operations
Lesson Objective
Topic: Number Operations
add and subtract decimals and to solve
To
problems involving decimals
Local Standards: ____________________________________
Example.
1 Finding Decimal Sums Find 6.8 1 4.65 1 2.125.
1
1
Step 1 Estimate 6.8 1 4.65 1 2.125 <
, or
6 . 8 0 0 d Line up the decimal points.
Step 2 Add.
4 . 6 5 0 d Write zeros so that all decimals have
the same number of digits to the right
2 . 1 2 5
!
of the decimal point.
.
Check for Reasonableness
The sum
is reasonable since it is close to
.
Quick Check.
1. Find 0.84 ! 2.0 ! 3.32. Estimate first.
14
Course 1 Lesson 1-7
Daily Notetaking Guide
Name
Class
Date
Examples.
2 Using Front-End Estimation A lemonade costs $1.79, sodas cost $1.29,
and water costs $1.49. Use front-end estimation to estimate the total cost of
buying one of each drink.
Step 1 Add the front-end digits. These
Step 2 Estimate the total cents.
are the the dollar amounts.
Then adjust dollar amounts.
$1.79
1.29
1 1.49
$1.79
1.29
! 1.49
$
$3
© Pearson Education, Inc., publishing as Pearson Prentice Hall.
All rights reserved.
The total cost is about $
!$
, or $
d about $
d about $
d about $
.
3 Finding a Difference First estimate and then find 16 " 8.79.
Estimate 16 " 8.79 !
"
, or
Write 16 with a
decimal point
and two zeros.
Rename 16 as 15 and
16.00
" 8.79
16.00
" 8.79
tenths.
Rename 10 tenths as 9 tenths
and 10
15 10
Check for Reasonableness The difference
close to
.
.
9
15 10 10
16.00
" 8.79
d Subtract.
is reasonable since it is
Quick Check.
2. Use front-end estimation to estimate the total cost of one small
popcorn and two large popcorns.
3. Use the graph at the right. How much greater is the women’s
record discus throw than the men’s throw?
60 m
70 m
80 m
76.80 m
74.08 m
Men's throw
Women's throw
Daily Notetaking Guide
Course 1 Lesson 1-7
15