There are three classes in the sixth grade, the first and second classes account for 2/3 of the whole grade, the first and third classes account for 60% of the whole grade, and the sixth grade has 40 students. How many students are there in each grade?
六年级有三个班，一、二两班人数占全年级人数的(2/3)，一、三两班人数占全年级人数的60%，六年级一班有40人．全年级有学生多少人？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/3) - (2/5)</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">40 / (4/15)</gadget>
<output>150</output>

<result>150</result>