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 5 chapters and video availability01 · Read and understand
What you will learn
- Create common fractional units before adding unlike fractions.
- Explain your method and check what the result means in the stated situation.
Before you start
Multi-digit operations, equivalent fractions, decimal place value, and rectangular area.
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
A recipe model uses 2/3 cup of one ingredient and 1/4 cup of another. What is their combined stated volume, assuming volumes add?
Why this math matters
Combine measurements by first expressing them with a common unit size. 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.
Add fractions with different units
PausedQuestion: Start with the question. Paused.
Question
Start with the question
A recipe model uses 2/3 cup of one ingredient and 1/4 cup of another. What is their combined stated volume, assuming volumes add?
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
Common unit: twelfths
Twelve is divisible by both three and four.
Connect the parts
2/3 = 8/12; 1/4 = 3/12
Rename both amounts without changing their values.
State and check the result
8/12 + 3/12 = 11/12 cup
Matching units let us add their counts.
The result
8/12 + 3/12 = 11/12 cup
Matching units let us add their counts.
Common mistakes to catch
- Unlike fractional pieces cannot be added by numerator alone.
- A common denominator need not be the smallest, although smaller units may be simpler.
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
Find 1/2 + 2/5.
Show a hint
Use tenths.
Reveal answer and explanation
9/10
Five tenths plus four tenths equals nine tenths.
Practice 2
Could twenty-fourths also be used for the main example?
Show a hint
Both denominators divide twenty-four.
Reveal answer and explanation
Yes
16/24 + 6/24 = 22/24, which simplifies to 11/12.
Take the idea with you
Combine measurements by first expressing them with a common unit size.
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: Subtract unlike fractions
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