Unit 2-Rates, Ratios, and Proportion

Notes

**Math 8: Chapter 2 – Ratios, Rates, and Proportions** --- **• Subtopic: Two-Term and Three-Term Ratios** **Vocabulary:** - **Two-term ratio:** Compares two quantities measured in the same units. Written as a:b or a to b. - **Three-term ratio:** Compares three quantities measured in the same units. Written as a:b:c or a to b to c. - **Part-to-part ratio:** Compares different parts of a group to each other. Does **NOT** include the total. - **Part-to-whole ratio:** Compares one part of a group to the total. --- **• Subtopic: Example 1 – Represent Ratios** A bag contains 20 marbles, as pictured. a) What is the two-term ratio of black to red marbles? Is this a part-to-part or part-to-whole ratio? **black : red = 10 : 4**. This is a **part-to-part ratio**. b) Compare the number of red marbles to the total number of marbles. Write the ratio as an equivalent fraction. Is this a part-to-part or part-to-whole ratio? **red : total = 4 : 20**. This is a **part-to-whole ratio** because it includes the total. c) What marbles are represented by the ratio 6 : 10? **6 ⇒ purple; 10 ⇒ black**. **purple : black** d) Write the three-term ratio comparing the red, purp...