Practice variation 3 of 3
Rates of change — Surface-area recognition
Your question
Explain briefly why for a sphere, and use it to find when .
This practice question was inspired by Question 11(f) in the 2024 NSW HSC Mathematics Extension 1 examination, © NESA. It is an original TestMum variation that practises the same mathematical idea, not an official NESA question.
Before you check
- Have you stated every choice or assumption?
- Can another student follow each line?
- Did you verify the final result independently?