It takes 5 seconds for a grasshopper to jump from the bottom to the top of the bamboo pole. It is known that it jumped 0.85 decimeters in the first second, and it jumped 0.5 decimeters more every second than the previous second. How high is this bamboo pole? (Please write down the process of solving the problem)
一个蚂蚱从竹竿底部跳向顶部一共需要5秒．已知第一秒跳了0.85分米，以后每秒都比上一秒多跳0.5分米，这根竹竿高几分米？(请写出解题过程)
<gadget id="calculator">0.85 * 5</gadget>
<output>4.25</output>

<gadget id="calculator">0.5 * 10</gadget>
<output>5</output>

<gadget id="calculator">4.25 + 5</gadget>
<output>9.25</output>

<result>9.25</result>