Learn with Amar
Teaching video
A teaching recording for this chapter has not been published yet. Start with the worked example below and explore the related animations where available.
Grade 1 chapters and video availability01 · Read and understand
What you will learn
- Use the same three numbers in related addition and subtraction facts.
- Explain your method and check what the result means in the stated situation.
Before you start
Recognizing small groups and saying counting words; an adult may read the prompts aloud.
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
There are 3 yellow and 5 green cubes. Write facts connecting 3, 5, and 8.
Why this math matters
Check an addition answer by undoing one part with subtraction. The worked example shows how to connect the situation, its mathematical representation, and a check on the result.
Set up the model
A useful answer starts with clear assumptions:
- Use the units, grouping rules, and reference whole stated in the question.
- Treat the supplied counts and measurements as exact within the classroom model, unless an estimate or a random outcome is requested.
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.
Connect addition and subtraction
PausedQuestion: Start with the question. Paused.
Question
Start with the question
There are 3 yellow and 5 green cubes. Write facts connecting 3, 5, and 8.
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 situation
3 + 5 = 8; 5 + 3 = 8
Both orders join the same two parts.
Connect the parts
8 − 3 = 5
Remove the yellow part to leave the green part.
State and check the result
8 − 5 = 3
Removing the other part leaves the first part.
The result
8 − 5 = 3
Removing the other part leaves the first part.
Common mistakes to catch
- Reversing subtraction does not preserve its answer.
- Use the whole as the first number in a take-away check.
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
Write a subtraction fact that checks 4 + 2 = 6.
Show a hint
Start from the whole six.
Reveal answer and explanation
6 − 4 = 2 or 6 − 2 = 4
Subtract either part to recover the other.
Practice 2
Does 2 − 6 = 4 belong to that family?
Show a hint
The whole goes first in these take-away facts.
Reveal answer and explanation
No
The valid facts start with six; two cannot lose six objects and leave four.
Take the idea with you
Check an addition answer by undoing one part with subtraction.
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: The equal sign means the same amount
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