The number of people who participated in the calligraphy group in Class 1 of four years accounted for 30% of the whole class. There were 42 students who did not participate, and 12 students joined the calligraphy group during the holiday. What percentage? (column solution)
四年一班原来参加书法小组的人数，占全班人数的30%，有42名同学没参加，假期里又有12名同学参加了书法小组，这时参加书法小组的总数占全班人数的百分之几？(列式解答)
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">42 / (7/10)</gadget>
<output>60</output>

<gadget id="calculator">60 - 42</gadget>
<output>18</output>

<gadget id="calculator">18 + 12</gadget>
<output>30</output>

<gadget id="calculator">30 / 60</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>