Unit 9: Measurement
Unit 9: Measurement
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Types of Angles:
Types of Angles:
- A right angle is an angle that forms a square corner (90°).
- A straight angle is an angle that forms a straight line (180°).
- An acute angle is an angle that is less than 90°.
- An obtuse angle is greater than a right angle (90°) but less than a straight angle (180°).
- A reflex angle is an angle that is greater than 180°.
Estimating Angles using Benchmarks
Estimating Angles using Benchmarks
When estimating an angle without using a protractor, it's important to use the following benchmarks as a guide:
When estimating an angle without using a protractor, it's important to use the following benchmarks as a guide:
- 180° is a straight angle and 90° is a right angle. By filling in these two benchmarks, you can see whether your angle is acute or obtuse!
- You can then look at the 45° or 135° benchmark which is half way between 0-90° and 90-180°.
You can use these benchmarks to estimate how big your angle is without using a protractor!
You can use these benchmarks to estimate how big your angle is without using a protractor!
- In this example, the blue (unknown) angle is >45° and <90°. One could estimate that the blue angle is ~65°, 70° or 75°.
How to Measure and Draw Angles Using a Protractor:
How to Measure and Draw Angles Using a Protractor:
How to measure an angle using a protractor
How to measure an angle using a protractor
How to draw an angle using a protractor
How to draw an angle using a protractor
How to Measure and Draw Reflex Angles:
How to Measure and Draw Reflex Angles:
Measuring a reflex angle
Measuring a reflex angle
Drawing a reflex angle (strategy 1)
Drawing a reflex angle (strategy 1)
Drawing a reflex angle (strategy 2)
Drawing a reflex angle (strategy 2)
Finding Missing Angles:
Finding Missing Angles:
Of a triangle:
Of a triangle:
Of a quadrilateral:
Of a quadrilateral:
Perimeter, Area and Volume:
Perimeter, Area and Volume:
- Perimeter: is when you measure the total length around the outside of a shape. To find the perimeter, you must add together the lengths of all sides.
- Area: the total space taken up by a flat 2D surface or shape of an object. To find the area, you must multiply length x width. It is measured in a unit squared.
- Ex. 10 cm2 or 50 km2
- Volume: the amount of space taken up by a 3D object. To find the volume, you must multiply the length x width x height. It is measured in a unit cubed.
- Ex. 10 cm3 or 50 m3
Equations:
Equations:
- Perimeter: P = l + w + l + w or P = 2(l) + 2(w)
- Area: A = l x w
- Volume: V = l x w x h
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