Big Ideas Math: Modeling Real Life, Grade 7
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5. Finding Unknown Angle Measures
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Exercise 34 Page 395

The sum of measures of angles around a point is 360^(∘).

∠ BAD=109^(∘) and ∠ CAD=111^(∘)

Practice makes perfect

Let's consider the given diagram.

We see that we have three angles around point A. The sum of measures of angles around a point equals 360^(∘), so we can write the following equation for x. 140^(∘)+ (2x+4)^(∘) + (2x+6)^(∘) = 360^(∘) Let's solve it!
140^(∘)+(2x+4)^(∘) + (2x+6)^(∘) = 360^(∘)
150^(∘) + 4x^(∘) = 360^(∘)
4x^(∘) = 210^(∘)
x^(∘) = 52.5^(∘)
Now, we can substitute x=52.5 into (2x+4)^(∘) and (2x+6)^(∘) to find the values of ∠ BAD and ∠ CAD.
Angle x=52.5 Measure
∠ BAD=(2x+4)^(∘) (2( 52.5)+4)^(∘) 109^(∘)
∠ CAD=(2x+6)^(∘) (2( 52.5)+6)^(∘) 111^(∘)