Lesson
7
Strategy Focus
Work Backward
MATH FOCUS: Addition and Subtraction with Decimals
Learn About It
Read the Problem The Romero family drove from Jacksonville, Florida to spend
3 days in Orlando. From there, they drove 235.1 miles to Miami.
Then they drove 156.5 miles to visit cousins in Key West.
Their total driving distance from Jacksonville to Key West was
543.5 miles. How far did they drive from Jacksonville to Orlando?
Reread Think about these questions as you read the problem.
What is happening in this problem?
●
Which distances are given in the problem?
●
What question do I have to answer?
●
Mark
the Text
Search for Information As you read the problem one more time, circle each distance.
Record Write the decimal that represents each distance.
It is
miles from Orlando to Miami.
It is
miles from Miami to Key West.
The Romero family drove
miles in all.
© Triumph Learning. OT113eIW7
Think about how you could use this data to solve the problem.
66 Unit 2 Using Fraction and Decimal Operations
Decide What to Do
You know two of the distances between the cities. You know the
total distance.
Ask How can I find the distance from Jacksonville to Orlando?
I can use the strategy Work Backward.
●
Start with the
total number
of miles for the
trip and work
backward.
I can start with the distance at the end of the trip. Then I can
subtract the distances I know to find the missing distance.
●
Use Your Ideas
Step 1
Write the total number of miles that the Romero
family drove.
Step 2
Subtract the distance from Key West to Miami from the
total distance driven. Remember to line up the numbers
you are subtracting by their decimal points.
543.5 miles −
Step 3
miles =
miles
Now subtract the distance from Miami to Orlando.
387.0 miles −
miles =
miles
Your answer is the distance from Jacksonville to Orlando.
So the Romero family drove
to Orlando.
Review Your Work
miles from Jacksonville
Use your answer to calculate the total distance driven. Check that
this number matches the number in the problem.
Why is Work Backward a good strategy for this problem?
© Triumph Learning. OT113eIW7
Conclude
67