There is a classroom with a length of 7.5 meters and a width of 8.5 meters. In this classroom, tiles with a side length of 5 decimeters are laid. How many such tiles are needed?
有一间教室长7.5米，宽8.5米，在这间教室里铺上边长为5分米的瓷砖，需要这样的瓷砖多少块？
<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">8.5 / (1/4)</gadget>
<output>34</output>

<gadget id="calculator">7.5 * 34</gadget>
<output>255</output>

<result>255</result>