Answer :

depends on the dimensions of the garden 
the most economical for resources is 10 ft*10 ft=100 sq ft
if 10 x 10 then fencing needed is 4 x 10 =40

if 5 x 20 then fencing needed is 5 x 2 + 20 x 2 = 50

so it depends on its shape, there are several answers if you stick with whole numbers and many more if you use fractions e.g 2.5 x 40

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