Çözüldü Optimization Problem - Differentiation - Order of Mathematical Operations

Test adaptation of a solved problem From New Jersey Institute of Technology:

If sand is being poured onto a conical pile at the rate of 3 cubic meters per second and the sand pile forms a right circular cone (with circular base on the ground) of height h and radius r, with the height equal to twice the base diameter, at what rate as meters per second is the height increasing when the pile becomes 6 meters high?

A) 3 / 4π
B) 3 / (4π)
C) 3π / 4
D) 4 / 3π
E) 4 / (3π)

Note: It is assumed that volume of the cone should be known by heart.


https://i.ibb.co/MSx1YVD/NJIT.png
https://math.njit.edu/sites/math/files/M111-F17-CE2-Solutions.pdf
(The last question)