Math Problem Statement

If m∠GEF is thirteen less than five times m∠DEG and m∠DEF = 149°, find m∠GEF.

Solution

The problem states:

  • mGEFm\angle GEF is thirteen less than five times mDEGm\angle DEG.
  • mDEF=149m\angle DEF = 149^\circ.

We are tasked with finding mGEFm\angle GEF.

Let's solve this step by step:

Step 1: Relationship Between Angles

The angle DEF\angle DEF is given as 149149^\circ. Notice that the figure suggests a straight line at point EE along the line segment EFEF. This means the sum of the angles GEF+DEG+DEF=180\angle GEF + \angle DEG + \angle DEF = 180^\circ (as the sum of angles on a straight line is 180180^\circ).

Thus, we have: mGEF+mDEG+149=180m\angle GEF + m\angle DEG + 149^\circ = 180^\circ mGEF+mDEG=31(subtracting 149 from both sides)m\angle GEF + m\angle DEG = 31^\circ \quad \text{(subtracting 149 from both sides)}

Step 2: Express mGEFm\angle GEF in Terms of mDEGm\angle DEG

According to the problem, mGEF=5mDEG13m\angle GEF = 5 \cdot m\angle DEG - 13.

Step 3: Substitute the Relationship

We now substitute mGEF=5mDEG13m\angle GEF = 5 \cdot m\angle DEG - 13 into the equation from Step 1: (5mDEG13)+mDEG=31(5 \cdot m\angle DEG - 13) + m\angle DEG = 31^\circ Simplifying: 5mDEG+mDEG13=315 \cdot m\angle DEG + m\angle DEG - 13 = 31^\circ 6mDEG13=316 \cdot m\angle DEG - 13 = 31^\circ Add 13 to both sides: 6mDEG=446 \cdot m\angle DEG = 44^\circ Divide by 6: mDEG=446=7.33m\angle DEG = \frac{44^\circ}{6} = 7.33^\circ

Step 4: Find mGEFm\angle GEF

Now, substitute mDEG=7.33m\angle DEG = 7.33^\circ into the expression for mGEFm\angle GEF: mGEF=57.3313=36.6513=23.65m\angle GEF = 5 \cdot 7.33^\circ - 13 = 36.65^\circ - 13 = 23.65^\circ

Final Answer:

mGEF23.65m\angle GEF \approx 23.65^\circ.

Let me know if you'd like more details or have any questions! Here are some follow-up questions to deepen your understanding:

  1. How do you identify angle relationships in geometric figures like this one?
  2. Why is the sum of angles on a straight line always 180180^\circ?
  3. What is the impact of solving for one angle using relationships with others?
  4. How do systems of equations help in finding unknown angles?
  5. Can you explain how the information given in word problems translates to equations?

Tip: Always start by writing down what is given and any geometric relationships (like angles on a straight line) to systematically approach the problem.

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Math Problem Analysis

Mathematical Concepts

Geometry
Angle Relationships
Linear Pair of Angles

Formulas

Sum of angles on a straight line = 180°
m∠GEF = 5 × m∠DEG - 13

Theorems

Linear Pair Angle Theorem

Suitable Grade Level

Grades 8-10