A rectangular parallelepiped glass tank measures 8.5dm in length, 6dm in width, 5dm in height and 3.5dm in water depth from the inside. After putting in a square log with a cross-sectional area of 25d㎡, the water overflows by 8.5dm**3. How long is the square log?
一个长方体的玻璃缸，从里面量长8.5dm，宽6dm，高5dm，水深3.5dm，投入一块横截面的面积是25d㎡的方木后，水溢出8.5dm**3，求投入的这块方木有多长？
<gadget id="calculator">8.5 * 6 * 5</gadget>
<output>255</output>

<gadget id="calculator">8.5 * 6 * 3.5</gadget>
<output>178.5</output>

<gadget id="calculator">8.5 - 178.5</gadget>
<output>-170</output>

<gadget id="calculator">255 + (-170)</gadget>
<output>85</output>

<gadget id="calculator">85 / 25</gadget>
<output>17/5 = around 3.4</output>

<result>17/5 = around 3.4</result>