All ACT Math Resources
Example Questions
Example Question #171 : Triangles
A triangle has a perimeter of inches with one side of length inches. If the remaining two sides have lengths in a ratio of , what is length of the shortest side of the triangle?
The answer is .
Since we know that the permieter is inches and one side is inches, it can be determined that the remaining two sides must combine to be inches. The ratio of the remaining two sides is which means 3 parts : 4 parts or 7 parts combined. We can then set up the equation , and divide both sides by which means . The ratio of the remaining side lengths then becomes or . We now know the 3 side lengths are .
is the shortest side and thus the answer.
Example Question #2 : How To Find The Length Of The Side Of Of An Acute / Obtuse Isosceles Triangle
In the standard coordinate plane, the points and form two vertices of an isosceles triangle. Which of the following points could be the third vertex?
To form an isosceles triangle here, we need to create a third vertex whose coordinate is between and . If a vertex is placed at , the distance from to this point will be . The distance from to this point will be the same.
Example Question #175 : Triangles
Note: Figure is not drawn to scale.
In the figure above, points are collinear and is a right angle. If and is , what is ?
Because is isosceles, equals or .
We know that add up to , so must equal or .
Example Question #231 : Act Math
A light beam of pure white light is aimed horizontally at a prism, which splits the light into two streams that diverge at a angle. The split beams each travel exactly from the prism before striking two optic sensors (one for each beam).
What is the distance, in feet, between the two sensors?
Round your final answer to the nearest tenth. Do not round until then.
This problem can be solved when one realizes that the light beam's split has resulted in an acute isosceles triangle. The triangle as stated has two sides of feet apiece, which meets the requirement for isosceles triangles, and having one angle of at the vertex where the two congruent sides meet means the other two angles must be and . The missing side connecting the two sensors, therefore, is opposite the angle.
Since we know at least two angles and at least one side of our triangle, we can use the Law of Sines to calculate the remainder. The Law of Sines says that for any triangle with angles and and opposite sides and :
.
Plugging in one of our angles (and its corresponding ft side) into this equation, as well as our angle (and its corresponding unknown side) into this equation gives us:
Next, cross-multiply:
--->
Now simplify and solve:
Rounding, we see our missing side is long.
Example Question #1 : Triangles
An isosceles triangle has a base of and an area of . What must be the height of this triangle?
.
Example Question #171 : Triangles
What is the height of an isosceles triangle which has a base of and an area of ?
The area of a triangle is given by the equation:
In this case, we are given the area () and the base () and are asked to solve for height ().
To do this, we must plug in the given values for and , which gives the following:
We then must multiply the right side, and then divide the entire equation by 2, in order to solve for :
Therefore, the height of the triangle is .
Example Question #175 : Triangles
There are two obtuse triangles. The obtuse angle of triangle one is . The sum of two angles in the second triangle is . When are these two triangles congruent?
Cannot be determined
The two triangles cannot be congruent
The two triangles must be congruent
When the obtuse angle is congruent to the smallest angle of the other triangle
When the sum of angle A and angle B in triangle 1 is equal to the sum of the corresponding angles in triangle 2
The two triangles cannot be congruent
In order for two obtuse triangles to be congruent, the sum of the two smaller angles must equal the sum of the two smaller angles of the second triangle. That is, excluding the obtuse angle.
The first triangle has an obtuse angle of . That means the sum of the other two angles is . The sum of the corresponding angles in triangle 2 is . Therefore, because is not equal to , the two obtuse triangles cannot be congruent.
Example Question #1 : How To Find An Angle In A Kite
Using the kite shown above, find the sum of the two remaining congruent interior angles.
The sum of the interior angles of any polygon can be found by applying the formula:
degrees, where is the number of sides in the polygon.
By definition, a kite is a polygon with four total sides (quadrilateral). The sum of the interior angles of any quadrilateral must equal: degrees degrees degrees. Additionally, kites must have two sets of equivalent adjacent sides & one set of congruent opposite angles.
To find the sum of the remaining two angles, determine the difference between degrees and the sum of the non-congruent opposite angles.
The solution is:
degrees
Thus, degrees is the sum of the remaining two opposite angles.
Check:
Example Question #2 : How To Find An Angle In A Kite
A kite has one set of opposite interior angles where the two angles measure and , respectively. Find the measurement for one of the two remaining interior angles in this kite.
Not enough information is provided
The sum of the interior angles of any polygon can be found by applying the formula:
degrees, where is the number of sides in the polygon.
By definition, a kite is a polygon with four total sides (quadrilateral). The sum of the interior angles of any quadrilateral must equal: degrees degrees degrees. Additionally, kites must have two sets of equivalent adjacent sides & one set of congruent opposite angles.
The missing angle can be found by finding the sum of the non-congruent opposite angles. Then divide the difference between degrees and the non-congruent opposite angles sum by :
This means that is the sum of the remaining two angles, which must be opposite congruent angles. Therefore, the measurement for one of the angles is:
Example Question #1 : How To Find An Angle In A Kite
A kite has one set of opposite interior angles where the two angles measure and , respectively. Find the measurement for one of the two remaining interior angles in this kite.
The sum of the interior angles of any polygon can be found by applying the formula:
degrees, where is the number of sides in the polygon.
A kite is a polygon with four total sides (quadrilateral). The sum of the interior angles of any quadrilateral must equal: degrees degrees degrees. Additionally, kites must have two sets of equivalent adjacent sides & one set of congruent opposite angles.
The missing angle can be found by finding the sum of the non-congruent opposite angles. Then divide the difference between degrees and the non-congruent opposite angles sum by :
This means that is the sum of the remaining two angles, which must be opposite congruent angles. Therefore, the measurement for one of the angles is: