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3
48/16.
Class 9 · English Medium · Cambridge · Mathematics
Ratio, proportion and algebra
Use algebraic fractions, variation and restrictions together.
About this lesson and its coverage
Original Kidemy Class 9 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
Factor before cancelling. Inverse-square variation y=k/x² changes by a factor of one quarter when x doubles. A restricted input stays excluded even if the simplified expression would have a value there.
Worked example
(x²−4)/(x+2)=x−2 for x≠−2. If y=36/x², y=9 when x=2.
- Identify the quantities and restrictions.
- Show a method with units or symbols.
- Check and explain the result.
Your written practice
Show your working on paper. Check your answer, then choose Next.
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x+4
Factor(x−4)(x+4); x≠4 remains.
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2
16/8.
Write in your own words. A guardian or teacher should review this response.
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x is not a factor of the entire numerator; the expression is 1+2/x.
Distinguish factors and terms.
Write in your own words. A guardian or teacher should review this response.
Show model answer and explanation
The denominator becomes9 times larger, so y becomes one ninth as large.
Use a scale factor.
Progress and browser storage
Notebook challenge, sources and further study
Apply the idea
Solve a variation problem and list the forbidden inputs.
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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