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Teaching video
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Grade 7 chapters and video availability01 · Read and understand
What you will learn
- Explain how to explain subtraction of a negative number.
- Solve the two practice problems and explain how the assumptions affect the answers.
Before you start
Additive inverses and signed addition.
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
Evaluate 4 − (−6) and explain the result as a difference between two number-line positions.
Why this math matters
Subtracting a number is adding its additive inverse; removing a negative change increases the result. Use final minus initial to compute signed change, then take its absolute value only if distance is requested.
Set up the model
A useful answer starts with clear assumptions:
- Subtraction means the first value minus the second.
- The number line increases to the right.
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.
Explain subtraction of a negative number
PausedQuestion: Start with the question. Paused.
Question
Start with the question
Evaluate 4 − (−6) and explain the result as a difference between two number-line positions.
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
4 − (−6) = 4 + 6
The additive inverse of −6 is +6.
Apply the relationship
4 + 6 = 10
A displacement from −6 to 4 is ten units to the right.
Check and interpret
check: −6 + 10 = 4
Adding the calculated difference to the subtracted position recovers the first position.
The result
check: −6 + 10 = 4
Adding the calculated difference to the subtracted position recovers the first position.
Common mistakes to catch
- The two minus signs have different roles: subtraction and a negative value.
- A difference can be negative; a distance cannot.
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
Calculate −3 − (−8).
Show a hint
Replace subtraction by addition of the opposite.
Reveal answer and explanation
5
−3 + 8 = 5.
Practice 2
Is 2 − 7 the same as 7 − 2?
Show a hint
Track the direction of each difference.
Reveal answer and explanation
No: −5 versus 5
Reversing the order changes the sign of a nonzero difference.
Take the idea with you
Use final minus initial to compute signed change, then take its absolute value only if distance is requested.
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: Use a pattern to justify a negative product
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