§-Quick questions
QLDSpecialist MathematicsUnit 4: Further calculus, and statistical inference
Quick questions on Implicit differentiation and related rates in QCE Specialist Mathematics Unit 4
2short 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 the chain rule for related rates?Show answer
If two quantities depend on time , their rates link through the chain rule. For a function of ,
What is differentiate, then substitute?Show answer
The crucial order is to differentiate first and substitute the specific values only afterward. Substituting a numerical value (such as a fixed radius) before differentiating treats a varying quantity as constant and loses its rate term, a frequent and heavily penalised error.
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