There was going to be a rope skipping competition in the school. Mr. Wang brought money to buy the rope skipping, and he brought 180 yuan. He went to the store and asked, the skipping rope that has been cut is 5 yuan, and the uncut rope is 1 yuan for 1 meter, and it costs 4 meters to make a skipping rope. Teacher Wang decided to buy ropes and cut them himself, so that he could buy more skipping ropes than buying cut ones.
学校里要举行跳绳比赛，王老师带钱去买跳绳，他带180元钱．他去店里一问，已经剪好的跳绳5元一根，没有剪好的是1米买1元，做一根跳绳要4米．王老师决定买绳子自己剪，这样可以比买剪好的跳绳多买多少根跳绳．
<gadget id="calculator">4 * 1</gadget>
<output>4</output>

<gadget id="calculator">180 / 4</gadget>
<output>45</output>

<gadget id="calculator">180 / 5</gadget>
<output>36</output>

<gadget id="calculator">45 - 36</gadget>
<output>9</output>

<result>9</result>