well, the base has four sides of 160 meters each, thus its perimeter is 160+160+160+160, or 640 meters.
well, a KILOmeter has 1000 meters, so
[tex] \bf 640\underline{m}\cdot \cfrac{km}{1000\underline{m}}\implies \cfrac{640km}{1000}\implies 0.64~km [/tex]
