The printing factory uses a batch of paper to bind the exercise books. It is planned to have 30 pages each, and 200 copies can be bound. The actual volume is 40 pages per volume, so how many volumes are bound less than planned? (Solve with ratio)
印刷厂用一批纸装订练习本，计划每本30页，可以装订200本．实际每本40页，这样比计划少装订多少本？(用比例解)
<gadget id="calculator">30 * 200</gadget>
<output>6_000</output>

<gadget id="calculator">6_000 / 40</gadget>
<output>150</output>

<gadget id="calculator">200 - 150</gadget>
<output>50</output>

<result>50</result>