On Arbor Day, the fourth grade planted 180 trees, which was (3/5) the number of fifth grade trees planted, and the fifth grade accounted for (2/3) the number of sixth grade trees. How many trees were planted by the sixth grade?
植树节那天，四年级植树180棵，是五年级植树棵数的(3/5)，五年级的棵数又占六年级的(2/3)，六年级植树多少棵？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">180 / (3/5) / (2/3)</gadget>
<output>450</output>

<result>450</result>