There are three pillars standing on the sports field. Seen from the outside, the lower section of the same length is covered by the wall. Comparing the parts seen above, the (4/5) of the A-pillar is equal to the B-pillar, and the (4/5) of the B-pillar ( 3/4) is equal to the C-pillar. It is known that the invisible part below is 1.8 meters. The ratio of it to the visible length of the C-pillar is 3:5. How many meters is the length of the A-pillar?
运动场上立着三根柱子，从场外看去，下面都有同样长的一段被墙遮住，把上面看见的部分进行比较，A柱的(4/5)与B柱相等，B柱的(3/4)与C柱相等，已知下面看不到的部分是1.8米，它与C柱看得见的长度的比是3：5，求A柱长多少米？
<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(5/3) / (3/4) / (4/5)</gadget>
<output>25/9 = around 2.777778</output>

<gadget id="calculator">1.8 * (25/9)</gadget>
<output>5</output>

<gadget id="calculator">5 + 1.8</gadget>
<output>6.8</output>

<result>6.8</result>