Welding 15 cuboid buckets without a lid with the bottom surface being a side length of 25 centimeters and a height of 4 decimeters with iron sheets, how many iron sheets should be used at least?
用铁皮焊15个底面是边长25厘米的正方形，高4分米的长方体无盖水桶，至少要用多少铁皮？
<gadget id="calculator">25 / 10</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(5/2) * (5/2)</gadget>
<output>25/4 = around 6.25</output>

<gadget id="calculator">(5/2) * 4 * 4</gadget>
<output>40</output>

<gadget id="calculator">(25/4) + 40</gadget>
<output>185/4 = around 46.25</output>

<gadget id="calculator">(185/4) * 15</gadget>
<output>2_775/4 = around 693.75</output>

<result>2_775/4 = around 693.75</result>