CAIE IGCSE Mathematics Extended E2.8.1 Express Direct and Inverse Proportion in Algebraic Terms and Use This Questions

Practise Extended CAIE IGCSE Mathematics by finding proportional constants, handling powers and roots, and combining relationships to calculate unknown quantities or changes.

Exam points

Translate direct or inverse proportion into y=kf(x) or y=k/f(x), including linear, square, square-root, cube and cube-root forms.
Use a known ordered pair to determine k, then calculate an unknown value or write one variable in terms of another.
Combine proportional relationships and calculate scale or percentage changes when a variable or power changes.

[Maximum number: 3]

y is inversely proportional to $\sqrt{x}$ .
When y=8, x=4.
Find y when x=49.

$2\frac27$ or $\frac{16}{7}$ oe

M2 for $y=\frac{16}{\sqrt{x}}$ or for $y\sqrt{49}=8\sqrt4$ oe.
M1 for $y=\frac{k}{\sqrt{x}}$ .

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CAIE IGCSE Mathematics Extended E2.8.1 Express Direct and Inverse Proportion in Algebraic Terms and Use This Questions question 1