Download Problem Solving Strategy

MNL04AWKXX_MG_Un
LESSON
itIcon 9.4
Name
Problem Solving Strategy
Work Backward
Sometimes you can work backward to solve
a problem.
Operation
Opposite
Operation
Bruce collected some sand dollars. He gave 10
to his younger sister. His friend Susan gave him
7 sand dollars. He put 4 back in the water. He
had 14 sand dollars left. How many did he collect?
Add
Subtract
Subtract
Add
Divide
Multiply
Multiply
Divide
•
First, write the steps of the problem in order
from left to right. Use numbers and operations
to describe the steps.
Number of
sand dollars
collected.
?
•
→
He gave
10 to
sister.
10
Susan
gave
him 7.
→
7
He put
4 back.
→
4
Number
left
→
14
←
14
Then, reverse the order and use the opposite
operations. Find the answer.
21
←
10
←
7
←
4
So, Bruce collected 21 sand dollars.
Reverse the order and use opposite operations. Find the answer.
1.
© Harcourt
2.
3.
?
→
3
→
8
→
11
→
27
43
←
3
←
8
←
11
←
27
?
→
11
→
25
→
52
38
←
11
←
25
←
52
Sasha and Chuck played a number game. Sasha
chose a number and subtracted 3. Next, she added
12. Then, she subtracted 20. Last, she added 11. The
result was 30. What number did Sasha begin with?
30
Reteach
RW47
LESSON 9.4
Name
Problem Solving Strategy
Work Backward
Sometimes you can work backward to solve
a problem.
Operation
Opposite
Operation
Bruce collected some sand dollars. He gave 10
to his younger sister. His friend Susan gave him
7 sand dollars. He put 4 back in the water. He
had 14 sand dollars left. How many did he collect?
Add
Subtract
Subtract
Add
Divide
Multiply
Multiply
Divide
•
First, write the steps of the problem in order
from left to right. Use numbers and operations
to describe the steps.
Number of
sand dollars
collected.
?
•
→
He gave
10 to
sister.
10
Susan
gave
him 7.
→
7
He put
4 back.
→
4
Number
left
→
14
←
14
Then, reverse the order and use the opposite
operations. Find the answer.
21
←
10
←
7
←
4
So, Bruce collected 21 sand dollars.
Reverse the order and use opposite operations. Find the answer.
1.
© Harcourt
2.
3.
?
→
3
→
8
→
11
→
27
43
←
3
←
8
←
11
←
27
?
→
11
→
25
→
52
38
←
11
←
25
←
52
Sasha and Chuck played a number game. Sasha
chose a number and subtracted 3. Next, she added
12. Then, she subtracted 20. Last, she added 11. The
result was 30. What number did Sasha begin with?
30
Reteach
RW47