Question: Reasoning in geometry
Topic 3: Parallel lines and angles
QUESTION 1 Find $x$, giving reasons.
a
$x^\circ$
$70^\circ$
position_hint: top-left; graph: two parallel horizontal lines cut by one rising transversal, with $x^\circ$ at the upper intersection below the top line and left of the transversal, and $70^\circ$ at the lower intersection above the bottom line and right of the transversal.
b
$x^\circ$
$120^\circ$
position_hint: top-center; graph: two slanted parallel lines cut by a horizontal transversal, with $x^\circ$ at the left intersection above the transversal and $120^\circ$ at the right intersection below the transversal.
c
$x^\circ$
$110^\circ$
position_hint: top-right; graph: two slanted parallel lines cut by a horizontal transversal, with $x^\circ$ at the left intersection below the transversal and $110^\circ$ at the right intersection below the transversal.
QUESTION 2 Find the value of the pronumeral, giving reasons.
a
y^\circ
x^\circ
$100^\circ$
position_hint: top-left; graph: two parallel horizontal lines cut by a rising transversal, with $y^\circ$ above the top line on the right, $x^\circ$ below the top line on the right, and $100^\circ$ above the bottom line on the left.
b
y^\circ
x^\circ
$75^\circ$
position_hint: top-center; graph: two parallel horizontal lines cut by a rising transversal, with $y^\circ$ above the top line on the left, $x^\circ$ above the top line on the right, and $75^\circ$ above the bottom line on the right.
c
$110^\circ$
x^\circ
y^\circ
position_hint: top-right; graph: two parallel horizontal lines cut by a rising transversal, with $110^\circ$ below the top line on the right, $x^\circ$ above the bottom line on the right, and $y^\circ$ below the bottom line on the left.
d
y^\circ
x^\circ
$45^\circ$
position_hint: center-left; graph: two parallel horizontal lines cut by a rising transversal, with $y^\circ$ below the top line on the left, $x^\circ$ below the top line on the right, and $45^\circ$ above the bottom line on the right.
e
y^\circ
x^\circ
$115^\circ$
position_hint: center; graph: two parallel horizontal lines cut by a rising transversal, with $y^\circ$ above the top line on the left, $x^\circ$ below the top line on the right, and $115^\circ$ above the bottom line on the left.
f
y^\circ
x^\circ
$70^\circ$
position_hint: center-right; graph: three parallel horizontal lines cut by a rising transversal, with $y^\circ$ below the top line on the left, $x^\circ$ below the top line on the right, and $70^\circ$ above the bottom line on the right.
QUESTION 3 Find the value of the pronumeral, giving reasons.
a
$x^\circ$
$108^\circ$
position_hint: lower-left; graph: two parallel slanted vertical lines standing on a horizontal base, with $x^\circ$ at the left bottom interior angle and $108^\circ$ at the right bottom interior angle.
b
$b^\circ$
$a^\circ$
$40^\circ$
position_hint: lower-center; graph: a horizontal line with a vertical line at center and a slanted line on each side marked parallel, with $b^\circ$ between the left slanted line and vertical, $a^\circ$ at the top of the vertical between it and the right slanted line, and $40^\circ$ at the lower right between the right slanted line and the baseline.
c
$c^\circ$
$b^\circ$
$50^\circ$
$a^\circ$
$a^\circ$
position_hint: lower-right; graph of a triangle between two parallel horizontal lines, with apex on the top line, $50^\circ$ inside the triangle near the apex, $c^\circ$ above-left of the apex on the top line, $b^\circ$ above-right of the apex on the top line, and $a^\circ$ at both base angles.
d
$30^\circ$
x^\circ
$60^\circ$
position_hint: lower-left; graph of two parallel horizontal lines with a broken transversal between them, $30^\circ$ at the upper intersection, $x^\circ$ at the middle kink, and $60^\circ$ at the lower intersection.
e
$80^\circ$
x^\circ
position_hint: lower-center; graph of two vertical parallel lines and two horizontal segments forming a U-shape, with $80^\circ$ at the lower-left corner and $x^\circ$ at the upper-right corner.
f
$50^\circ$
$a^\circ$
$40^\circ$
position_hint: lower-right; graph of several rays meeting at a vertex, with $50^\circ$ between the left slanted ray and the middle rising ray, $a^\circ$ at the vertex between the left slanted ray and the lower-right ray, and $40^\circ$ between the right rising ray and the lower-right ray.
Question 1 a
$x^\circ = 50^\circ$
Question 1 b
$m^\circ = 110^\circ$
Question 1 c
$x^\circ = 50^\circ$
$y^\circ = 130^\circ$
Question 1 d
$x^\circ = 120^\circ$
Question 1 e
$x^\circ = 70^\circ$
Question 1 f
$x^\circ = 40^\circ$
Question 2 a
$x^\circ = 120^\circ$
Question 2 b
$a^\circ = 25^\circ$
Question 2 c
$x^\circ = 30^\circ$
Question 2 d
$y^\circ = 55^\circ$
Question 2 e
$a^\circ = 30^\circ$
Question 2 f
$a^\circ = 95^\circ$
$b^\circ = 95^\circ$
$c^\circ = 85^\circ$
Question 3 a
$x^\circ = 60^\circ$
Question 3 b
$x^\circ = 80^\circ$
$y^\circ = 35^\circ$
Question 3 c
$x^\circ = 90^\circ$
Graph shape position_hint=top-left: intersecting lines forming vertical opposite angles, with one angle marked $50^\circ$ and adjacent angles labeled $x^\circ$ and $y^\circ$.
1. **Problem statement:** Find $x$ in the given figure where two parallel horizontal lines are cut by a transversal, with angles $x^\circ$ and $70^\circ$ as shown.
2. **Relevant rule:** When two parallel lines are cut by a transversal, alternate interior angles are equal.
3. **Apply the rule:** Since $x^\circ$ and $70^\circ$ are alternate interior angles,
$$x = 70$$
4. **Check for vertical angles:** The problem states $x^\circ$ is adjacent to $50^\circ$ in the top-left position hint, indicating vertical opposite angles.
5. **Vertical angles are equal:** So,
$$x = 50$$
6. **Conclusion:** The value of $x$ is $50^\circ$ based on vertical angles.
**Final answer:**
$$\boxed{50^\circ}$$