All ACT Math Resources
Example Question #1 : How To Find An Angle In A Quadrilateral
The interior angles of a quadrilateral are , , , and . What is the measure of the smallest angle?
The key piece of knowledge is that the interior angles of a quadrilateral add up to .
Therefore, the following equation can be set up:
When we combine like terms, we get:
We then subtract 71 from both sides:
and then divide both sides by 17:
It should be noted that the problem is not finished. The question asks for the measure of the smallest angle. We have only found . If students do not read the question carefully, they may end up selecting as their answer, which would be incorrect.
The smallest angle will either be or . To find out, simply plug in for :
Because , the measure of the smallest angle is .
Example Question #2 : How To Find An Angle In A Quadrilateral
bisects . If then, in degrees, what is the value of ?
A rectangle has two sets of parallel sides with all angles equaling 90 degrees.
Since bisects into two equal parts, this creates an isosceles triangle .
Therefore . The sum of the angles in a triangle is 180 degrees.
Example Question #3 : How To Find An Angle In A Quadrilateral
The rhombus above is bisected by two diagonals.
If and then, in degrees, what is the value of the ?
Note: The shape above may not be drawn to scale.
A rhombus is a quadrilateral with two sets of parallel sides as well as equal opposite angles. Since the lines drawn inside the rhombus are diagonals, and are each bisected into two equal angles.
Therefore, , which creates a triangle in the upper right quadrant of the kite. The sum of angles in a triangle is 180 degreees.
Since is only half of ,
Example Question #191 : Quadrilaterals
If and , then, in degrees, what is the value of ?
Note: The figure may not be drawn to scale.
In a rhombus, opposite angles are equal to each other. Therefore we can set and equal to one another and solve for :
A rhombus, like any other quadrilateral, has a sum of angles of 360 degrees.