class is 40 minutes, reviewing (1/5) of the total time, new lessons (3/8) of the total time, and the rest is practice time. What fraction of the total time was spent practicing?
一节课40分钟，复习用了总时间的(1/5)，新课用了总时间的(3/8)，剩余的是练习时间．练习时间用了总时间的几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (1/5) - (3/8)</gadget>
<output>17/40 = around 0.425</output>

<result>17/40 = around 0.425</result>