Class 61 subscribes to mathematics journals. The number of people who subscribe to newspapers accounts for 40% of the number of grades, the number of people who subscribe to mathematics journals accounts for 40% of the number of subscribers, and the number of people who subscribe to Chinese newspapers accounts for 3/4 of the number of subscribers. There are 15 students, how many people are there in the whole grade?
六1班订阅数学报，订阅报纸人数占年级人数的百分之四十，订数学报人数占订阅人数的百分之四十，订语文报占订阅人数的四分之三，两报都订的有15人，全年级有几人？
<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) - 1</gadget>
<output>-3/5 = around -0.6</output>

<gadget id="calculator">(3/4) + (-3/5)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">15 / (3/20) / (2/5)</gadget>
<output>250</output>

<result>250</result>