Chunlin Primary School carried out tree planting activities, of which 40% were planted by the sixth graders and 15% were planted by the fifth graders. A total of 220 trees were planted by the two graders. How many trees did Chunlin Primary School plant in this tree planting activity?
春林小学开展植树活动，其中40%是六年级植的，15%是五年级植的，两个年级一共植树220棵．这次植树活动春林小学一共植树多少棵？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(2/5) + (3/20)</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">220 / (11/20)</gadget>
<output>400</output>

<result>400</result>