Question 46·Easy·Lines, Angles, and Triangles
In , the measure of is twice the measure of , and the measure of is . What is the measure, in degrees, of ?
For triangle-angle questions where one angle is a multiple of another, assign a variable (like ) to the smallest angle and write the others in terms of that variable (e.g., , ). Then use the fact that the three interior angles sum to 180° to create and solve a simple linear equation, and finally plug back to get the specific angle the question asks for. This keeps your work organized and minimizes mistakes under time pressure.
Hints
Use the triangle angle sum
Remember that the three interior angles in any triangle always add up to . How can you use this fact here?
Introduce a variable for one angle
Let angle be degrees. How can you write angle in terms of if it is twice angle ?
Write and solve an equation
Using the fact that angle is , write an equation for based on . Then solve for and use it to find angle .
Desmos Guide
Compute angle Q using an expression
In a Desmos expression line, type (180 - 24) / 3 and look at the value Desmos gives; this represents the measure of angle in degrees.
Use angle Q to find angle P
In a new Desmos line, type 2 * ((180 - 24) / 3) to represent twice angle . The value Desmos shows is the measure of angle in degrees; compare this to the answer choices.
Step-by-step Explanation
Translate the word relationship into algebra
We are told that in :
- angle is twice angle .
- angle is .
Let the measure of angle be degrees. Then the measure of angle is degrees, and angle is .
Use the triangle angle-sum rule
In any triangle, the sum of the three interior angles is .
So for we have:
Substitute the expressions in terms of :
Solve for the value of x (angle Q)
Combine like terms on the left:
Subtract 24 from both sides:
Divide both sides by 3:
So angle measures .
Find angle P and match it to the choices
Angle is twice angle , so its measure is:
So angle measures , which corresponds to choice C.