Benchmark Instructional Guide
Connecting Benchmarks/Horizontal Alignment
Terms from the K-12 Glossary
- Acute Angle
- Obtuse Angle
- Right Angle
Purpose and Instructional Strategies
The purpose of this benchmark is to build understanding that angles can be measured. Students have experience identifying acute, obtuse, and right angles (MA.4.GR.1.1
). Through instruction in this benchmark, students will attach precise measurements to their informal understanding of the angles they have explored.
- Students will also estimate angle measures based on their growing familiarity of the size of angles according to the benchmark angles 30°, 45°, 60°, 90° and 180°.
- Instruction should allow students to draw angles of all sizes, including situations where they must make angles that are larger than their protractor or their piece of paper. This will ensure that students have an understanding that the angle measure does not change even if the length of the rays do.
- Instruction should use explicit and direct instruction to show students how to use a protractor (standard or circle) to measure and draw angles. Using circle protractors helps students explore reflex angles.
- Instructional time should also be spent breaking apart angles into smaller angles so that students build understanding that angle measures are additive.
Common Misconceptions or Errors
- Students that have difficulty using a protractor to measure. Assist students with this misconception as they may:
- use the centimeter ruler or inch ruler instead of the baseline when measuring the angles.
- measure the length of each ray and find the sum of the lengths.
- not correctly line up the angle to be measured on the protractor.
Strategies to Support Tiered Instruction
- Instruction includes using a right angle, 90 degrees measure, as a benchmark to estimate angle measures prior to measuring with a protractor. The teacher provides students with a right angle to overlap with the angles they are measuring as a way to compare their size.
- For example, when given an angle, students will determine if the angle is 90 degrees, greater than 90 degrees, or less than 90 degrees. Students then measure the angle using a protractor and determine if their measurement makes sense based on their estimate.
- The teacher provides angles that have a baseline ray labeled so that students know which ray to line up with the baseline on the protractor and begin their measurement from. Students explain how they will use the protractor to measure the angle (which set of numbers they will use to measure and how they know where to stop measuring).
- For example, the teacher provides an angle similar to the one shown below. Students line up the baseline of the protractor with the ray on the angle that is labeled as the baseline. Students will start measuring with the set of numbers that begins with 0 at the end of the ray and follow the measurements around to the point where the other ray intersects with the protractor.
Instructional Task 1
- Use a protractor to find the measure of each indicated angle.
Instructional Item 1
- Which angles when added together make a right angle?
*The strategies, tasks and items included in the B1G-M are examples and should not be considered comprehensive.