Welcome to the Unit 1.1 Tree Trunk Problem!
This unit focuses on the CAHSEE problem:
The diameter of a tree trunk varies directly with the age of the tree. A 45-year-old tree has a trunk diameter of 18 inches. What is the age of a tree that has a trunk diameter of 20 inches?
A. 47 years
B. 50 years
C. 63 years
D. 90 years
This question has challenged up to 65% of students who have taken the CAHSEE exam. As you progress through this unit, you will deepen your content knowledge on approaches to proportional reasoning and develop instructional strategies to assist students in mastering these kinds of problems.
The major California Mathematics Content standards addressed in this question include:
Number Sense (6th) 1.0 Students compare and order positive and negative fractions, decimals, and mixed numbers. Students solve problems involving fractions, ratios, proportions, and percentages.
Algebra and Functions (6th) 1.0 Students write verbal expressions and sentences as algebraic expressions and equations; they evaluate algebraic expressions, solve simple linear equations, and graph and interpret their results.
Algebra and Functions (7th) 1.0 Students express quantitative relationships by using algebraic terminology, expressions, equations, inequalities, and graphs.
Successful completion of PD-ROMi is a prerequisite to this unit.
In Unit 1.1: The Tree Trunk Problem, you will
- Deepen your understanding of mathematical concepts in Algebra, including:
- Using unit rate, ratios, and proportions; and
- Solving direct variation problems through unit rates and proportions.
- Develop skills in new instructional strategies, including
- The importance of the flow of the lesson;
- Use of poetry and literature to support teaching and learning of mathematics; and
- Teaching vocabulary.
- Apply your new knowledge and skills in the Lesson Plan Project.
What you will see:
What you will do:
In addition, your Online Facilitator will be checking your responses for accuracy and completion.
Unit 1.1 The Tree Trunk Problem should take approximately 10-15 hours, depending on your technology skills and knowledge of instructional strategies. You may complete this unit on your own time, but each strand is expected to be completed by a specific deadline. This will allow your Online Facilitator to provide collective support and will facilitate your collaboration with your colleagues. It will also insure that you complete the unit by the course endpoint.

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