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20
2.5×8.
Class 8 · English Medium · Cambridge · Mathematics
Ratio, proportion and algebra
Model proportional change and algebraic fractions.
About this lesson and its coverage
Original Kidemy Class 8 progression. This level has its own text, examples and questions. Curriculum versions share the progression; complete board-specific coverage still needs specification matching and additional material.
Learn the idea
A direct-proportion graph passes through the origin. Algebraic fractions can be simplified by cancelling common factors, not separate terms in a sum. Retain any excluded denominator values.
Worked example
y=3x has constant y/x=3. (x²−9)/(x−3)=x+3 for x≠3.
- Identify the quantities and restrictions.
- Show a method with units or symbols.
- Check and explain the result.
Your written practice
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5
60/12.
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2/3
Cancel the common nonzero factor3a.
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The original denominator is zero at 3.
Retain the original domain.
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C=100;40 is fixed cost and 12n is the amount varying with n.
Interpret, not just substitute.
Progress and browser storage
Notebook challenge, sources and further study
Apply the idea
Compare a proportional and a fixed-fee model using a table and graph.
Review with a guardian or teacher
- Use the stated evidence or givens.
- Show reasoning rather than only a result.
- Review and explain one correction.
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