Problem 1 :
In the figure shown below, m∠1 = 105°. Find the measures of the remaining angles.
Solution :
∠1 and ∠2 form a linear pair and they are supplementary.
m∠1 + m∠2 = 180°
105° + m∠2 = 180°
m∠2 = 75°
∠1 and ∠3 are vertical angles and they are equal.
m∠3 = m∠1
m∠3 = 105°
∠2 and ∠4 are vertical angles and they are equal.
m∠4 = m∠2
m∠4 = 75°
∠1 and ∠5 are corresponding angles and they are equal.
m∠5 = m∠1
m∠5 = 105°
∠2 and ∠6 are corresponding angles and they are equal.
m∠6 = m∠2
m∠6 = 75°
∠3 and ∠7 are corresponding angles and they are equal.
m∠7 = m∠3
m∠7 = 105°
∠4 and ∠8 are corresponding angles and they are equal.
m∠8 = m∠4
m∠8 = 75°
Problem 2 :
In the figure shown below, m∠2 = 78°. Find the measures of ∠6, ∠10 and ∠14.
Solution :
In the figure above, lines m and n are parallel, p and q are parallel.
∠2 and ∠6 are corresponding angles and they are equal.
m∠6 = m∠2
Substitute m∠2 = 78°.
m∠6 = 78°
∠6 and ∠14 are corresponding angles and they are equal.
m∠14 = m∠6
Substitute m∠6 = 78°.
m∠14 = 78°
∠10 and ∠14 are corresponding angles and they are equal.
m∠10 = m∠14
Substitute m∠14 = 78°.
m∠10 = 78°
Therefore,
m∠6 = 78°
m∠10 = 78°
m∠14 = 78°
Problem 3 :
In the figure shown below, lines m and n are parallel and p is transversal. Find the value of x.
Solution :
In the figure above m and n are parallel and p is transversal. Angles 5x° and (3x + 28)° are corresponding angles and they are equal.
5x° = (3x + 28)°
5x = 3x + 28
Subtract 3x from each side.
2x = 28
Divide each side by 2.
x = 14
Problem 4 :
In the figure shown below, solve for x.
Solution :
In the figure above, two parallel lines are intersected by another two parallel lines.
y° and 106° are corresponding angles and they are equal.
y° = 106°
(4x + 6)° and y° are corresponding angles and they are equal.
(4x + 6)° = y°
Substitute y° = 106°.
(4x + 6)° = 106°
4x + 6 = 106
Subtract 6 from each side.
4x = 100
Divide each side by 4.
x = 25
Find the angle x in each question below. Give reasons for your answer
Problem 5 :
CF and GJ are parallel lines and BL is the transversal.
Alternate interior angles are equal. Then x = 59.
Problem 6 :
Solution :
AK and BL are parallel lines. Alternate exterior angles are equal.
<KHI = 72 (alternate exterior angle)
x and 72 linear pairs. Then, x + 72 = 180
x = 180 - 72
x = 108
Problem 7 :
Solution :
AC and DG are parallel lines. Alternate exterior angles are equal.
<ABE + <EBF + <BFE = 180 (cointerior angles)
41 + 60 + x = 180
101 + x = 180
x = 180 - 101
x = 79
Problem 8 :
Solution :
<DEB = 134
<DEB and <EBA are co-interior angles.
<EBA = 180 - 134
<EBA = 46
<BEF = 46
Alternate interior angles will be equal.
<EBF = <EFB
<BEF + <EBF + <EFB = 180
<BEF + <EBF + <EBF = 180
<BEF + 2<EBF = 180
46 + 2<EBF = 180
2<EBF = 180 - 46
2<EBF = 134
<EBF = 134/2
= 67
<ABE + <EBF + <FBC = 180
46 + 67 + x = 180
113 + x = 180
x = 180 - 113
= 67
Problem 9 :
Solution :
BE and FI are parallel lines.
<ACD = 48 (because vertically opposite angles)
<CDA = 77 (Corresponding angles)
In triangle ACD,
<ACD + <CDA + <DAC = 180
48 + 77 + <DAC = 180
125 + <DAC = 180
<DAC = 180 - 125
<DAC = 55 degree
Problem 10 :
Solution :
CF and AB are parallel lines.
<BDE = <DBA = 76 (alternate interior angles are equal)
<EBD = 76 (Equal sides will make equal angles)
Using exterior angle theorem,
<BEF = <BDE + <EBD
= 76 + 76
= 152
x = 28
So, the value of x is 28 degree.
Problem 11 :
Solution :
AB and CD are parallel lines and 108 and angle x are corresponding angles, they must be equal.
x = 108
x + y = 180
y = 180 - 108
y = 72
Problem 12 :
Solution :
EF and GH are parallel lines and x and y are corresponding angles.
x = 88
x = y = 88 (corresponding angles)
Problem 13 :
Solution :
IJ and KL are parallel lines and x and 51 are co-interior angles.
x + 51 = 180
x = 180 - 51
x = 129
100 and y are corresponding angles.
y = 100
y + z = 180
100 + z = 180
z = 180 - 100
z = 80
Problem 14 :
Solution :
x and 62 are alternate interior angles since MN and OP are parallel lines.
x = 62
Problem 15 :
Solution :
Since QR and ST are parallel lines, x and y are corresponding angles.
UV and WX are parallel lines, x and 71 are alternate interior angles. So, they are equal.
x = 71
x + y = 180
71 + y = 180
y = 180 - 71
y = 109
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