NS 2.2
Find the sum or difference of two whole numbers up to three
digits long.
UNDERLYING SKILLS AND CONCEPTS:
addition;
subtraction
Problem Solving: Choose the Operation
a
K
ey Ide
You can use what you know about addition and
subtraction to solve problems.
E x am p l E
1
B – © CSL Associates, Inc. All rights reserved.
Cindy had 47¢. She spent 25¢.
How much money does she have left?
First you need to determine whether to add or subtract. Since she
spent money she would have less money.
That shows to subtract.
47¢
– 25¢
22¢
She has 22¢ left.
E x am p l E
2
Jessie had 56¢. He earned 35¢ more.
How much money does he have now?
Should you add or subtract?
Since he earned money, he will have more money.
That shows to add.
56¢
+ 35¢
91¢
He now has 91¢.
Chapter 12 – Lesson 3
page 139
Name
P RAC T I C E
First tell whether to add or subtract. Then solve the problem.
1
Nancy has 44¢. She spent
20¢. How much money does
she have left?
2
Marty had 75¢. Then he
found 10¢. How much
money does he have now?
24¢
3
85¢
There were 16 birds in the
tree. 7 flew away. How many
are left?
There were 17 children on
the playground. 5 more
came to the playground.
How many children are
there altogether?
4
9 birds
5
Dana had a box of 48
crayons. She broke 4 of
them. How many are left?
6
44 crayons
David had 64 colors of
paints. He got 10 new colors.
How many colors does he
have now?
74 colors
Math
Reasoning
7
Choose the Operation
MR 2.3
Jo had 65¢. She spent 15¢. Then she earned 25¢. How much
money does she have now?
75 ¢
page 140
Chapter 12 – Lesson 3
B – © CSL Associates, Inc. All rights reserved.
22 children
Name
P RAC T I C E
First tell whether to add or subtract. Then solve the problem.
1
Nora has 87¢. She spent
23¢. How much money does
she have left?
2
Marty had 55¢. Then he
found 25¢. How much
money does he have now?
subtract; 64¢
3
add; 80¢
There were 16 ants on the
apple. 7 crawled away. How
many are left?
4
subtract; 9 ants
There were 16 children on
the playground. 9 more
came to the playground.
How many children are there
altogether?
5
Dana had a box of 64
crayons. She broke 14 of
them. How many are left?
6
subtract; 50 crayons
David had 36 colors of
paints. He got 48 new colors.
How many colors does he
have now?
add; 84 colors
Math
Reasoning
7
Choose the Operation
MR 2.3
Joe had 85¢. He spent 25¢. Then he earned 50¢. How much
money does he have now?
$1.10
page 94
Home Resource and Homework
Chapter 12 Lesson 3
B – © CSL Associates, Inc. All rights reserved.
add; 25 children
MCX94TEG2Ch01_30.v9.4.1 2/19/01 19:48 Page 257
Name
P RAC T I C E
First tell whether to add or subtract. Then solve the problem.
1
Nancy has 44¢. She spent
20¢. How much money does
she have left?
2
Marty had 75¢. Then he
found 10¢. How much
money does he have now?
subtract; 24¢
3
add; 85¢
There were 16 birds in the
tree. 7 flew away. How many
are left?
There were 17 children on
the playground. 5 more
came to the playground.
How many children are
there altogether?
4
subtract; 9 birds
B – © CSL Associates, Inc. All rights reserved.
add; 22 children
5
Dana had a box of 48
crayons. She broke 4 of
them. How many are left?
6
subtract; 44 crayons
David had 64 colors of
paints. He got 10 new colors.
How many colors does he
have now?
add; 74 colors
Math
Reasoning
7
Choose the Operation
MR 2.3
Jo had 65¢. She spent 15¢. Then she earned 25¢. How much
money does she have now?
75 ¢
Chapter 12 – Lesson 3
Student Book Page
page 140
Name
P RAC T I C E
First tell whether to add or subtract. Then solve the problem.
1
Nora has 87¢. She spent
23¢. How much money does
she have left?
2
Marty had 55¢. Then he
found 25¢. How much
money does he have now?
subtract; 64¢
3
add; 80¢
There were 16 ants on the
apple. 7 crawled away. How
many are left?
4
subtract; 9 ants
There were 16 children on
the playground. 9 more
came to the playground.
How many children are there
altogether?
5
Dana had a box of 64
crayons. She broke 14 of
them. How many are left?
6
subtract; 50 crayons
David had 36 colors of
paints. He got 48 new colors.
How many colors does he
have now?
add; 84 colors
Math
Reasoning
7
Choose the Operation
MR 2.3
Joe had 85¢. He spent 25¢. Then he earned 50¢. How much
money does he have now?
$1.10
page 94
Home Resource and Homework
Chapter 12 Lesson 3
B – © CSL Associates, Inc. All rights reserved.
add; 25 children