There are 15 people participating in the art group in the school, the number of the calligraphy group is 2/3 of the art group, and the number of the math group is 2/5 of the calligraphy group. How many people are there in the math group?
学校参加美术小组的有15人，书法小组的人数是美术小组的(2/3)，数学小组的人数是书法小组的(2/5)，数学小组有多少？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">15 * (2/3) * (2/5)</gadget>
<output>4</output>

<result>4</result>