There are 18 girls in Class 61 of Boai Primary School, accounting for 3/7 of the whole class, and the number of students in Class 61 is 1/20 of the whole school. How many students are there in the whole school?
博爱小学六1班有女生18人，占全班人数的(3/7)，六1班学生人数又是全校人数的(1/20)，全校有学生多少人？
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">18 / (3/7) / (1/20)</gadget>
<output>840</output>

<result>840</result>