The areas of the two triangles are equal. The bottom of the first piece is 15 decimeters long and 4 decimeters high. The bottom of the first piece is three times that of the second piece. How many decimeters is the height of the second piece?
两个三角形面积相等．第一块底边长15分米，高4分米，第一块的底是第二块的3倍，第二块的高是多少分米？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

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

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 * (2/5)</gadget>
<output>12</output>

<result>12</result>