The 90th anniversary of the founding of the Communist Party of China, a total of 90 students from the fifth and sixth grades of a certain school participated, and the number of participants in the fifth grade was 4/5 of the number of participants in the sixth grade. How many students in the fifth grade participated in the art performance?
迎建党90周年文艺汇演，某校五六年级一共有90名同学参加，五年级参加的人数是六年级参加人数的(4/5)，五年级有多少人参加文艺汇演？
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 + (4/5)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">90 / (9/5)</gadget>
<output>50</output>

<gadget id="calculator">90 - 50</gadget>
<output>40</output>

<result>40</result>