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Box Volume Baffle (Posted on 2014-11-05) Difficulty: 3 of 5
The respective length, breadth and height of the rectangular cuboid R1 is A+2, B+2 and C+2 and the respective length, breadth and height of the rectangular cuboid R2 is A, B and C.

It is known that:

(i) The volume of R1 is precisely twice that of R2, and:
(ii) Each of A, B and C is a positive integer with A ≤ B ≤ C

Determine the maximum value of C.

No Solution Yet Submitted by K Sengupta    
Rating: 3.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: Probable solution (is my reasoning sensible?) | Comment 2 of 5 |
(In reply to Probable solution (is my reasoning sensible?) by Jer)

Jer:


I don't think your reasoning is quite right, but I think you came up with the right answer.

 In order to maximize C, we want 
(A+2)(B+2)/AB to be as large as possible but still under 2.

If A = 3 and B = 11, then (A+2)(B+2)/AB ~ 1.97

It is quite clear from your work that A and B must both be between 3 and 11.  Seems like there is still room for improvement, but a quick excel check didn't find anything better. 

If A = B = 5, then (A+2)(B+2)/AB  is only 1.96
If A = 4 and B = 7 then (A+2)(B+2)/AB  is only ~ 1.93

So, I like your answer! 

  Posted by Steve Herman on 2014-11-06 07:31:06
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