The Triangle Cookie Company in the historic district of the Old Town has been making its perfectly round cookies for decades and selling them in their signature isosceles triangle boxes, with three rows separated by straight red packing strips, following these two packaging rules:
An enterprising employee decides to try improving the packing efficiency--measured by the ratio of the area occupied by the cookies to the area of the box--by relaxing the first rule to "All of the cookies in the same row are exactly the same size." This means that each row could have cookies of a different diameter than the other rows. The cookies will be packaged in an isosceles triangle box with suitable dimensions, so that it obeys the second rule.
Let be the packing efficiency. Then, approximately, what's the maximum possible percentage increase in obtained by adjusting the sizes of the round cookies instead of keeping them all the same?
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Let s be the slope of the sides of the triangle, and let r 3 = 1 , r 2 , r 1 be the radii of the cookies, with the bottom row being all unit circles. The length of the base and the area of the triangle are
b = 2 ( 2 + s 1 ( 1 + 1 + s 2 ) )
A = 2 1 b ( 2 1 b s )
The radii then works out to
r 3 = 1
r 2 = ( 1 + s 1 ( 1 + 1 + s 2 ) ) ( 2 + s 1 ( − 1 + 1 + s 2 ) ) r 3
r 1 = ( 0 + s 1 ( 1 + 1 + s 2 ) ) ( 1 + s 1 ( − 1 + 1 + s 2 ) ) r 2
The ratio of area of cookies to the area of the triangle then becomes
R = A π ( 3 r 3 2 + 2 r 2 2 + r 1 2 )
With s as the variable, by numerical means the maximum value for R can be found to be
R = 0 . 7 2 0 1 3 1 0 5 7 8 …
r 1 = 0 . 9 6 7 1 9 7 7 8 7 …
r 2 = 0 . 9 8 7 3 2 7 6 6 7 …
r 3 = 1
s = 1 . 9 3 5 1 5 6 …
while in the original case it was
R = 0 . 7 1 9 9 8 8 9 6 8 9 …
r 1 = 1
r 2 = 1
r 3 = 1
s = 2
so that the percent improvement is
1 0 0 ( 0 . 7 1 9 9 8 8 9 6 8 9 … 0 . 7 2 0 1 3 1 0 5 7 8 … − 0 . 7 1 9 9 8 8 9 6 8 9 … ) = 0 . 0 1 9 7 3 4 9 . . . % ≃ 0 . 0 2 %