Eric Nicholas K's answer to Georgia Jansen's Secondary 4 A Maths Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
1st
We are given the circumference of the circle. We must extract the radius out of this data.

Subsequently, we define the area of the circle and then evaluate dA/dr when r = the radius which you obtained earlier.

You are also given that dA/dt.

By the chain rule,

dA/dt = dA/dr * dr/dt

Sub in values of dA/dt and dA/dr.
Eric Nicholas K
Eric Nicholas K
5 years ago
Sorry, dr/dt = 1/12 cm/s. Correction.