A school bought 90 meters of rope and used 9 meters to make 5 skipping ropes. According to this calculation, how many skipping ropes can be made with the remaining rope? (Solve with ratio)
某学校买来90米绳子，用9米做5根跳绳，照这样计算，余下的绳子还可以做多少根跳绳？(用比例解)
<gadget id="calculator">90 - 9</gadget>
<output>81</output>

<gadget id="calculator">81 * 5</gadget>
<output>405</output>

<gadget id="calculator">405 / 9</gadget>
<output>45</output>

<result>45</result>