Xiaoqiang's distance from home to school is 1800m, usually 24 minutes. One day he was in a hurry and walked 15m more per minute than usual. How many minutes did Xiaoqiang take to get from home to school less than usual?
小强从家到学校路程是1800m，平时走24分钟．一天他有急事，每分钟比平时多走15m，这天小强从家到学校比平时少用多少分钟？
<gadget id="calculator">1_800 / 24</gadget>
<output>75</output>

<gadget id="calculator">75 + 15</gadget>
<output>90</output>

<gadget id="calculator">1_800 / 90</gadget>
<output>20</output>

<gadget id="calculator">24 - 20</gadget>
<output>4</output>

<result>4</result>