body{margin:0;} noscript{z-index: 10000; position: fixed; display: block; height: 100%; width: 100%; background: #fff;} noscript .fa{font-size: 40px; display:block; color: #daa520;} noscript div{margin-top: 6%; padding-left: 20px; padding-right: 20px; text-align: center;} ! You must have JavaScript enabled to use this site.

Big Ideas Math: Modeling Real Life, Grade 7

BI

Big Ideas Math: Modeling Real Life, Grade 7 View details

5. Finding Unknown Angle Measures

Continue to next subchapter

Exercise 10 Page 392

The sum of measure of angles around a point equals 360^(∘).

x=60

Practice makes perfect

First, let's take a look at the given diagram.

We have several angles around point J. Two of them, ∠ KJN and ∠ NJM have their measures written as algebraic expressions in terms of x. Also, ∠ MJK is a right angle, so its measure is 90^(∘). Since the sum of measures of angles around a point equals 360^(∘), we can write the following equation for x. m ∠ KJN + m ∠ NJM + m ∠ MJK = 360^(∘) ⇓ (2x-10)^(∘) + (2x+40)^(∘) + 90^(∘) = 360^(∘) Let's solve it!

(2x-10)^(∘) +(2x+40^(∘))+90^(∘) = 360^(∘)

Add terms

4x^(∘) +120^(∘) = 360^(∘)

LHS-120^(∘)=RHS-120^(∘)

4x^(∘) = 240^(∘)

.LHS /4.=.RHS /4.

x^(∘) = 60^(∘)

Subchapter links

Try It p.390-392

Self-Assessment for Concept & Skills p.392

Self-Assessment for Problem Solving p.393

Review & Refresh p.394

Concept, Skills, & Problem Solving p.394-396