6th Grade Math Textbook, Progress

Substitute simpler numbers to help you choose the operation(s) to use.

13.17 cm^313 2.08 cm^32 1.19 cm^31

Start with 13. Subtract the amount of the decrease, 2.

Then add the amount of the increase, 1.

13 
 2 11 cm^311  1 12 cm^3

Work backward to check the answer.

amount increased original amount

(12.28 cm^3 
1.19 cm) 2.08 cm^3 13.17 cm^3

amount after 2 weeks amount decreased

The answer checks.

Visualize yourself in the problem above as you reread it.

List the facts and the question.

Facts: 13.17 cm^3 at the beginning

2.08 cm^3 decrease

1.19 cm^3 increase

Question:What was the volume of pollutants after two weeks?

A scientist conducted a series of experiments

with a liter of polluted water. At the beginning of

the experiment, the pollutants reached a volume

of 13.17 cubic centimeters (cm^3 ). Over the next

two weeks there was a decrease of 2.08 cm^3

and then an increase of 1.19 cm^3. What was

the volume of pollutants after two weeks?

Problem-Solving Strategy:

Use Simpler Numbers

2-7

Now solve the problem using the actual numbers.


13.17 cm^3 
11.09 cm^3


 0 2.08 cm^3  0 1.19 cm^3


11.09 cm^3 
12.28 cm^3

After two weeks the volume of pollutants was 12.28 cm^3.

2.0 8 cm^3

decrease

1.19 cm^3

increase

13 .17 cm^3

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