Learn with Amar
Teaching video
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Grade 7 chapters and video availability01 · Read and understand
What you will learn
- Explain how to distinguish supplementary and vertical angles.
- Solve the two practice problems and explain how the assumptions affect the answers.
Before you start
A straight angle measures 180°.
Keep paper nearby. Read the question once for the context, then again to identify what is known and what you need to find.
Start with a question
Two lines intersect. One angle is 65°. Find the adjacent angle and the vertically opposite angle.
Why this math matters
Adjacent angles on a straight line add to 180°, while opposite vertical angles at intersecting lines are equal. Mark shared sides and straight lines before deciding whether to add angles or set them equal.
Set up the model
A useful answer starts with clear assumptions:
- The figure consists of two distinct straight lines.
- Adjacent means sharing a side with the given angle.
02 · Work through the example
Follow the reasoning, one step at a time.
Try to predict the next step before reading it. After each calculation, explain why the operation makes sense and how it helps answer the original question.
Work through it with Amar
See this example unfold.
The complete worked example, one idea at a time.
Distinguish supplementary and vertical angles
PausedQuestion: Start with the question. Paused.
Question
Start with the question
Two lines intersect. One angle is 65°. Find the adjacent angle and the vertically opposite angle.
Before you calculate
Read what is known and what you need to find. Make a prediction before moving to the first calculation.
Starts paused. Play advances through the full text at a reading pace; pause whenever you need more time. Previous, Next, and the phase buttons let you set your own pace. Playback pauses when this walkthrough leaves the screen or you switch tabs.
Your device’s reduced-motion setting keeps each phase still. Manual controls remain available. The full written solution stays below.
Represent the quantities
adjacent + 65° = 180°
The adjacent pair fills a straight angle.
Apply the relationship
adjacent = 115°
Subtract the known angle from 180°.
Check and interpret
vertical opposite = 65°
The opposite angle is supplementary to the same 115° angle, so it matches the original.
The result
vertical opposite = 65°
The opposite angle is supplementary to the same 115° angle, so it matches the original.
Common mistakes to catch
- Supplementary angles total 180°; complementary angles total 90°.
- Vertical angles are opposite, not side-by-side.
03 · Practice independently
Try it before revealing the answer.
Use paper or a calculator as needed. Write your units and reasoning, then open the hint or explanation to check your approach.
Practice 1
Two supplementary angles have measures y° and 3y°. Find them.
Show a hint
Their sum is 180°.
Reveal answer and explanation
45° and 135°
4y = 180 gives y = 45, then 3y = 135.
Practice 2
An angle is 32°. What is its complement?
Show a hint
Complementary angles total 90°, not 180°.
Reveal answer and explanation
58°
90 − 32 = 58.
Take the idea with you
Mark shared sides and straight lines before deciding whether to add angles or set them equal.
04 · Reflect and continue
Can you explain it in your own words?
Before moving on, explain the main idea without looking at the worked example. Try both practice questions, check your reasoning, and name one mistake you now know how to avoid. Return to a step if you still need support.
Up next: Find a probability through its complement
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