The escalator is moving from bottom to top at a uniform speed, and two impatient children are going upstairs from the escalator. It is known that the boy walks 20 steps per minute, and the girl walks 15 steps per minute. As a result, it takes the boy 5 minutes to reach the upstairs and the girl 6 minutes to reach the upstairs. Q: How many steps does the escalator have?
自动扶梯以均匀速度由下往上行驶着，两位性急的孩子要从扶梯上楼．已知男孩每分钟走20级梯级，女孩每分钟走15级梯级，结果男孩用了5分钟到达楼上，女孩用了6分钟到达楼上．问：该扶梯共有多少级？
<gadget id="calculator">20 * 5</gadget>
<output>100</output>

<gadget id="calculator">15 * 6</gadget>
<output>90</output>

<gadget id="calculator">100 - 90</gadget>
<output>10</output>

<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<gadget id="calculator">10 / 1</gadget>
<output>10</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<gadget id="calculator">30 * 5</gadget>
<output>150</output>

<result>150</result>