| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.51 |
| Score | 0% | 70% |
If angle a = 49° and angle b = 52° what is the length of angle d?
| 142° | |
| 139° | |
| 122° | |
| 131° |
An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:
d° = b° + c°
To find angle c, remember that the sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 49° - 52° = 79°
So, d° = 52° + 79° = 131°
A shortcut to get this answer is to remember that angles around a line add up to 180°:
a° + d° = 180°
d° = 180° - a°
d° = 180° - 49° = 131°
Order the following types of angle from least number of degrees to most number of degrees.
right, acute, obtuse |
|
acute, obtuse, right |
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right, obtuse, acute |
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acute, right, obtuse |
An acute angle measures less than 90°, a right angle measures 90°, and an obtuse angle measures more than 90°.
When two lines intersect, adjacent angles are __________ (they add up to 180°) and angles across from either other are __________ (they're equal).
supplementary, vertical |
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vertical, supplementary |
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acute, obtuse |
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obtuse, acute |
Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).
A right angle measures:
180° |
|
45° |
|
360° |
|
90° |
A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.
What is the area of a circle with a radius of 3?
| 9π | |
| 81π | |
| 25π | |
| 6π |
The formula for area is πr2:
a = πr2
a = π(32)
a = 9π