The school divides the tree planting task between the sixth grade and the fifth grade according to the ratio of 5:3. In the sixth grade, 180 trees were planted, exceeding 20% of the original allocation. How many trees were originally planned to be planted in the sixth and fifth grades?
学校把植树任务按5：3分给六年级和五年级．六年级栽了180棵，超过原分配的20%．原计划六年级、五年级分别栽多少棵树？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">180 / (6/5)</gadget>
<output>150</output>

<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">150 / (5/3)</gadget>
<output>90</output>

<result>90</result>