Use tiles to stick the wall, the wall is 4 meters long and 3 meters high. There are currently two specifications of tiles with a side length of 3 decimeters, a length of 5 decimeters, and a width of 3 decimeters. Which specification of tiles to choose will not waste materials? How many tiles of this kind do you need?
用磁砖贴墙面，墙面长4米，高3米．现有边长3分米和长5分米、宽3分米两种规格的磁砖，选哪种规格的磁砖不浪费材料？需要这种磁砖多少块？
<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">40 * 30</gadget>
<output>1_200</output>

<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">1_200 / 15</gadget>
<output>80</output>

<result>80</result>