Strategy Focus
4 Guess, Check, and Revise
Lesson
MATH FOCUS: All Operations with Decimals and Fractions
Learn
Read the Problem Daria’s current workout routine uses 936 calories. She wants to
change to a combination of swimming and running. Swimming uses
about 7.5 calories per minute. Running uses about 8.7 calories per
minute. Daria is going to exercise for two hours. She wants her new
workout to use the same number of calories as her current workout.
How many minutes should she spend swimming?
Reread As you read the problem again, look for details that will help
you solve it.
How will Daria’s new workout be the same as her current workout?
●
How will her new workout be different from her current workout?
●
What do I need to find out?
●
Mark
the Text
Search for Information Read the problem one more time. Circle facts that describe Daria’s
new workout.
Record Use the details from the problem to complete the statements.
Daria is going to exercise for
Swimming uses about
Running uses about
Her new workout will use
hours.
calories per minute.
calories per minute.
calories.
© Triumph Learning. OT115eIW4
There is a lot information in the problem. Choose a problem-solving
strategy that will help you find a good place to start.
42 Unit 1 Using Whole Numbers, Decimals, and Fractions
Decide What to Do
You know how many calories are used per minute for each of two
exercises. You know the total time Daria will exercise.
Ask How can I find the number of minutes Daria should swim?
I can use the strategy Guess, Check, and Revise. I can guess how many
minutes she swims, and use that to find the time she runs. Then I can
multiply the number of minutes by calories per minute for each type
of exercise.
●
Then I can add to check the total calories in the workout. If my answer
matches Daria’s goal, I am done. If not, I can revise my guess to get closer.
●
Use Your Ideas
Step 1
A table can help you keep track of each guess you make.
Guess
Minutes
Swimming
1
60
2
70
Calories
Used by
Swimming
Calories
Used by
Running
60
450
522
too high
50
525
435
too high
Minutes
Running
Total
Calories
Step 2
Use the result from your first guess to choose a new guess.
Record your calculations in the table.
Step 3
Keep guessing until the number of calories from Daria’s
new workout matches the number of calories from her
current workout.
Daria should spend
Review Your Work
Make sure
your guesses
for minutes
swimming +
minutes
running =
2 hours, which
is 120 minutes.
minutes swimming in her new workout.
© Triumph Learning. OT115eIW4
Does the new workout have the correct total number of minutes? Does it
have the correct total number of calories?
Recognize Why is 60 minutes a reasonable first guess for the number of
minutes Daria swims?
43