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VICSpecialist MathematicsQuick questions

Unit 4: Calculus

Quick questions on Related rates of change: VCE Specialist Mathematics Unit 4

8short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What are variables and rates?
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Given dVdt=100 cm3/s\frac{dV}{dt} = 100\ \text{cm}^3/\text{s}; wanted drdt\frac{dr}{dt} when r=5 cmr = 5\ \text{cm}.
What is differentiate with respect to time?
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Using the chain rule,
What is substitute the instant?
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Put dVdt=100\frac{dV}{dt} = 100 and r=5r = 5:
What is not reducing to one variable?
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In cone problems, use similar triangles to write the radius in terms of the height before differentiating, so only one rate is unknown.
What is wrong sign?
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A decreasing quantity has a negative rate. Watch for "draining" or "shrinking" wording.
What is q1?
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Write the related-rates equation linking the area and radius of a circle. [2 marks]
What is q2?
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A cube's edge grows at 2 cm/s2\ \text{cm/s}. Find dVdt\frac{dV}{dt} when the edge is 4 cm4\ \text{cm}. [3 marks]
What is q3?
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Why must you differentiate before substituting the instant? [1 mark]

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