Use 4 identical cups to hold water, the height of the water surface is 4 cm, 5 cm, 7 cm and 8 cm respectively, what is the average height of the water surface of these 4 cups in cm?
用4个同样的杯子装水，水面高度分别是4厘米、5厘米、7厘米和8厘米，这4个杯子水面平均高度是多少厘米．
<gadget id="calculator">4 + 5 + 7 + 8</gadget>
<output>24</output>

<gadget id="calculator">24 / 4</gadget>
<output>6</output>

<result>6</result>