Lesson 5 answers

Lesson 5
NYS COMMON CORE MATHEMATICS CURRICULUM
8β€’4
T
Exit Ticket Sample Solutions
For each of the following problems, write an equation and solve.
1.
Given a right triangle, find the measures of all of the angles, in degrees, if one angle is a right angle and the measure
of the second angle is six less than seven times the measure of the third angle.
Let 𝒙 represent the measure of the third angle. Then, πŸ•π’™ βˆ’ πŸ” can represent the measure of the second angle. The
sum of the two angles in the right triangle will be πŸ—πŸŽ°.
πŸ•π’™ βˆ’ πŸ” + 𝒙 = πŸ—πŸŽ
πŸ–π’™ βˆ’ πŸ” = πŸ—πŸŽ
πŸ–π’™ βˆ’ πŸ” + πŸ” = πŸ—πŸŽ + πŸ”
πŸ–π’™ = πŸ—πŸ”
πŸ–
πŸ—πŸ”
𝒙=
πŸ–
πŸ–
𝒙 = 𝟏𝟐
The third angle is 𝒙 and therefore measures 𝟏𝟐°. Replacing 𝒙 with 𝟏𝟐 in πŸ•π’™ βˆ’ πŸ” gives πŸ•(𝟏𝟐) βˆ’ πŸ” = πŸ–πŸ’ βˆ’ πŸ” = πŸ•πŸ–.
Therefore, the measure of the second angle is πŸ•πŸ–°. The measure of the third angle is πŸ—πŸŽ°.
2.
In a triangle, the measure of the first angle is six times a number. The measure of the second angle is nine less than
the first angle. The measure of the third angle is three times the number more than the measure of the first angle.
Determine the measure of each angle in degrees.
Let 𝒙 be the number. Then, the measure of the first angle is πŸ”π’™, the measure of the second angle is πŸ”π’™ βˆ’ πŸ—, and the
measure of the third angle is πŸ‘π’™ + πŸ”π’™. The sum of the measures of the angles in a triangle is πŸπŸ–πŸŽ°.
πŸ”π’™ + πŸ”π’™ βˆ’ πŸ— + πŸ‘π’™ + πŸ”π’™ = πŸπŸ–πŸŽ
πŸπŸπ’™ βˆ’ πŸ— = πŸπŸ–πŸŽ
πŸπŸπ’™ βˆ’ πŸ— + πŸ— = πŸπŸ–πŸŽ + πŸ—
πŸπŸπ’™ = πŸπŸ–πŸ—
𝟐𝟏
πŸπŸ–πŸ—
𝒙=
𝟐𝟏
𝟐𝟏
𝒙=πŸ—
Replacing 𝒙 with πŸ— in πŸ”π’™ gives πŸ”(πŸ—) = πŸ“πŸ’. Replacing 𝒙 with πŸ— in πŸ”π’™ βˆ’ πŸ— gives πŸ”(πŸ—) βˆ’ πŸ— = πŸ“πŸ’ βˆ’ πŸ— = πŸ’πŸ“. Replacing
𝒙 with πŸ— in πŸ‘π’™ + πŸ”π’™ gives πŸ“πŸ’ + πŸ‘(πŸ—) = πŸ“πŸ’ + πŸπŸ• = πŸ–πŸ. Therefore, the angle measures are πŸ“πŸ’°, πŸ’πŸ“°, and πŸ–πŸ°.
Note to teacher: There are several ways to solve problems like these. For example, a student may let π‘₯ be the measure
of the first angle and write the measure of the other angles accordingly. Either way, make sure that students are
defining their symbols and correctly using the properties of equality to solve.
Lesson 5:
Writing and Solving Linear Equations
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This file derived from G8-M4-TE-1.3.0-09.2015
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Lesson 5
NYS COMMON CORE MATHEMATICS CURRICULUM
8β€’4
T
Problem Set Sample Solutions
Students practice writing and solving linear equations.
For each of the following problems, write an equation and solve.
1.
The measure of one angle is thirteen less than five times the measure of another angle. The sum of the measures of
the two angles is πŸπŸ’πŸŽ°. Determine the measure of each angle in degrees.
Let 𝒙 be the measure of the one angle. Then, the measure of the other angle is πŸ“π’™ βˆ’ πŸπŸ‘.
𝒙 + πŸ“π’™ βˆ’ πŸπŸ‘ = πŸπŸ’πŸŽ
πŸ”π’™ βˆ’ πŸπŸ‘ = πŸπŸ’πŸŽ
πŸ”π’™ βˆ’ πŸπŸ‘ + πŸπŸ‘ = πŸπŸ’πŸŽ + πŸπŸ‘
πŸ”π’™ = πŸπŸ“πŸ‘
𝒙 = πŸπŸ“. πŸ“
Since one angle measure is 𝒙, it is πŸπŸ“. πŸ“°. Replacing 𝒙 with πŸπŸ“. πŸ“ in πŸ“π’™ βˆ’ πŸπŸ‘ gives
πŸ“(πŸπŸ“. πŸ“) βˆ’ πŸπŸ‘ = πŸπŸ’πŸŽ βˆ’ πŸπŸ“. πŸ“ = πŸπŸπŸ’. πŸ“. Therefore, the other angle measures πŸπŸπŸ’. πŸ“°.
2.
An angle measures seventeen more than three times a number. Its supplement is three more than seven times the
number. What is the measure of each angle in degrees?
Let 𝒙 be the number. Then, the measure of one angle is πŸ‘π’™ + πŸπŸ•. The measure of the other angle is πŸ•π’™ + πŸ‘. Since
the angles are supplementary, the sum of their measures will be πŸπŸ–πŸŽ.
πŸ‘π’™ + πŸπŸ• + πŸ•π’™ + πŸ‘ = πŸπŸ–πŸŽ
πŸπŸŽπ’™ + 𝟐𝟎 = πŸπŸ–πŸŽ
πŸπŸŽπ’™ + 𝟐𝟎 βˆ’ 𝟐𝟎 = πŸπŸ–πŸŽ βˆ’ 𝟐𝟎
πŸπŸŽπ’™ = πŸπŸ”πŸŽ
𝒙 = πŸπŸ”
Replacing 𝒙 with πŸπŸ” in πŸ‘π’™ + πŸπŸ• gives πŸ‘(πŸπŸ”) + πŸπŸ• = πŸ”πŸ“. Replacing 𝒙 with πŸπŸ” in πŸ•π’™ + πŸ‘ gives
(πŸπŸ”) + πŸ‘ = 𝟏𝟏𝟐 + πŸ‘ = πŸπŸπŸ“. Therefore, the angle measures are πŸ”πŸ“° and πŸπŸπŸ“°.
3.
The angles of a triangle are described as follows: βˆ π‘¨ is the largest angle; its measure is twice the measure of βˆ π‘©.
The measure of ∠π‘ͺ is 𝟐 less than half the measure of βˆ π‘©. Find the measures of the three angles in degrees.
Let 𝒙 be the measure of βˆ π‘©. Then, the measure of βˆ π‘¨ is πŸπ’™, and the measure of ∠π‘ͺ is
measures of the angles must be πŸπŸ–πŸŽ°.
𝒙 + πŸπ’™ +
πŸ‘π’™ +
Lesson 5:
𝒙
𝟐
βˆ’ 𝟐. The sum of the
𝒙
βˆ’ 𝟐 = πŸπŸ–πŸŽ
𝟐
𝒙
βˆ’ 𝟐 + 𝟐 = πŸπŸ–πŸŽ + 𝟐
𝟐
𝒙
πŸ‘π’™ + = πŸπŸ–πŸ
𝟐
πŸ”π’™ 𝒙
+ = πŸπŸ–πŸ
𝟐 𝟐
πŸ•π’™
= πŸπŸ–πŸ
𝟐
Writing and Solving Linear Equations
This work is derived from Eureka Math β„’ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G8-M4-TE-1.3.0-09.2015
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This work is licensed under a
Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Lesson 5
NYS COMMON CORE MATHEMATICS CURRICULUM
8β€’4
T
πŸ•π’™ = πŸ‘πŸ”πŸ’
𝒙 = πŸ“πŸ
Since 𝒙 is the measure of βˆ π‘©, then βˆ π‘© is πŸ“πŸ°. Replacing 𝒙 with πŸ“πŸ in πŸπ’™ gives 𝟐(πŸ“πŸ) = πŸπŸŽπŸ’. Therefore, the
measure of βˆ π‘¨ is πŸπŸŽπŸ’°. Replacing 𝒙 with πŸ“πŸ in
is πŸπŸ’°.
4.
𝒙
𝟐
βˆ’ 𝟐 gives
πŸ“πŸ
𝟐
βˆ’ 𝟐 = πŸπŸ” βˆ’ 𝟐 = πŸπŸ’. Therefore, the measure of ∠π‘ͺ
A pair of corresponding angles are described as follows: The measure of one angle is five less than seven times a
number, and the measure of the other angle is eight more than seven times the number. Are the angles congruent?
Why or why not?
Let 𝒙 be the number. Then, the measure of one angle is πŸ•π’™ βˆ’ πŸ“, and the measure of the other angle is πŸ•π’™ + πŸ–.
Assume they are congruent, which means their measures are equal.
πŸ•π’™ βˆ’ πŸ“ = πŸ•π’™ + πŸ–
πŸ•π’™ βˆ’ πŸ•π’™ βˆ’ πŸ“ = πŸ•π’™ βˆ’ πŸ•π’™ + πŸ–
βˆ’πŸ“ β‰  πŸ–
Since βˆ’πŸ“ β‰  πŸ–, the angles are not congruent.
5.
The measure of one angle is eleven more than four times a number. Another angle is twice the first angle’s
measure. The sum of the measures of the angles is πŸπŸ—πŸ“°. What is the measure of each angle in degrees?
Let 𝒙 be the number. The measure of one angle can be represented with πŸ’π’™ + 𝟏𝟏, and the other angle’s measure
can be represented as 𝟐(πŸ’π’™ + 𝟏𝟏) = πŸ–π’™ + 𝟐𝟐.
πŸ’π’™ + 𝟏𝟏 + πŸ–π’™ + 𝟐𝟐 = πŸπŸ—πŸ“
πŸπŸπ’™ + πŸ‘πŸ‘ = πŸπŸ—πŸ“
πŸπŸπ’™ + πŸ‘πŸ‘ βˆ’ πŸ‘πŸ‘ = πŸπŸ—πŸ“ βˆ’ πŸ‘πŸ‘
πŸπŸπ’™ = πŸπŸ”πŸ
𝒙 = πŸπŸ‘. πŸ“
Replacing 𝒙 with πŸπŸ‘. πŸ“ in πŸ’π’™ + 𝟏𝟏 gives πŸ’(πŸπŸ‘. πŸ“) + 𝟏𝟏 = πŸ“πŸ’ + 𝟏𝟏 = πŸ”πŸ“. Replacing 𝒙 with πŸπŸ‘. πŸ“ in 𝟐(πŸ’π’™ + 𝟏𝟏)
gives 𝟐(πŸ’(πŸπŸ‘. πŸ“) + 𝟏𝟏) = 𝟐(πŸ“πŸ’ + 𝟏𝟏) = 𝟐(πŸ”πŸ“) = πŸπŸ‘πŸŽ. Therefore, the measures of the angles are πŸ”πŸ“° and πŸπŸ‘πŸŽ°.
6.
Three angles are described as follows: βˆ π‘© is half the size of βˆ π‘¨. The measure of ∠π‘ͺ is equal to one less than two
times the measure of βˆ π‘©. The sum of βˆ π‘¨ and βˆ π‘© is πŸπŸπŸ’°. Can the three angles form a triangle? Why or why not?
𝒙
𝒙
𝟐
Let 𝒙 represent the measure of βˆ π‘¨. Then, the measure of βˆ π‘© is , and the measure of ∠π‘ͺ is 𝟐 ( ) βˆ’ 𝟏 = 𝒙 βˆ’ 𝟏.
𝟐
The sum of the measures of βˆ π‘¨ and βˆ π‘© is πŸπŸπŸ’.
𝒙
= πŸπŸπŸ’
𝟐
πŸ‘π’™
= πŸπŸπŸ’
𝟐
πŸ‘π’™ = πŸπŸπŸ–
𝒙+
𝒙 = πŸ•πŸ”
Since 𝒙 is the measure of βˆ π‘¨, then βˆ π‘¨ is πŸ•πŸ”°. Replacing 𝒙 with πŸ•πŸ” in
𝒙
𝟐
gives
πŸ•πŸ”
𝟐
= πŸ‘πŸ–; therefore, the measure of βˆ π‘©
is πŸ‘πŸ–°. Replacing 𝒙 with πŸ•πŸ” in 𝒙 βˆ’ 𝟏 gives πŸ•πŸ” βˆ’ 𝟏 = πŸ•πŸ“, therefore the measure of ∠π‘ͺ is πŸ•πŸ“°. The sum of the three
angle measures is πŸ•πŸ”° + πŸ‘πŸ–° + πŸ•πŸ“° = πŸπŸ–πŸ—°. Since the sum of the measures of the interior angles of a triangle must
equal πŸπŸ–πŸŽ°, these angles do not form a triangle. The sum is too large.
Lesson 5:
Writing and Solving Linear Equations
This work is derived from Eureka Math β„’ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G8-M4-TE-1.3.0-09.2015
55
This work is licensed under a
Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.