A piece of iron wire 90 cm long, cut half of it the first time, the rest (1/3) the second time, the remaining (1/4) the third time, and the fourth time For the remaining (1/5), cut off the remaining (1/6) for the fifth time, ..., and cut it in this way, how many centimeters are left after the 19th cut.
一根长90厘米的铁丝，第一次剪掉它的一半，第二次剪掉剩下的(1/3)，第三次剪掉剩下的(1/4)，第四次剪掉剩下的(1/5)，第五次剪掉剩下的(1/6)，…，照此方法剪下去，剪完第19次后还剩下多少厘米长．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">90 * (1/20)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>