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A circular cylinder , open at 1 end, has radius r cm and external surface area 27pi cm^2.

Show that the volume of the cylinder V cm3 is given by V = pi/2 (27r - r^3)

Given that r can vary, find the stationary value of V (I got 84.8cm, answer given is 84.4 cm)

Would someone please confirm the accuracy for me. Thanks

***By the way, are real numbers referring to any numbers?***

alright. ill attach my soln.

yes. you are right btw.

The soln in the book might have used pi=3.14, while you might have used the pi value of 3.141592654(found in your calculator).

Hi,

Thanks to OHSheet for his solution. It's fine to leave the answer in exact form, and we'll not have to worry about accuracy :) Thanks!

Cheers,
Wen Shih

about leaving in exact form, let us follow O level instructions

Hi,

Thanks for pointing out, for I am not familiar with O-level instructions.

I have checked that A-level H2 maths does not have the point in bullet 1.

Thanks again!

Cheers,
Wen Shih

welcome.........

exception is where special angles are being used, for example,2 pi = 360 degrees in deg and 6.28 rad, pi can be used, but decimal will be preferred