There are 150 students in the fourth grade of Heping Street Primary School, and 20% fewer students in the fifth grade than in the fourth grade. The total number of students in the two grades accounts for exactly 60% of the total number of students in the school. How many students are there in the whole school?
和平街小学四年级有学生150人，五年级学生比四年级少20%，两个年级的学生总数正好占全校人数的60%，全校共有学生多少人？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">150 * (4/5)</gadget>
<output>120</output>

<gadget id="calculator">150 + 120</gadget>
<output>270</output>

<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">270 / (3/5)</gadget>
<output>450</output>

<result>450</result>