The third grade planted 20 trees, and the fourth grade planted three times as many trees as the third grade. How many trees were planted in the fourth grade?
三年级植树20棵，四年级植树棵树是三年级的3倍，四年级植树多少棵．
<gadget id="calculator">20 * 3</gadget>
<output>60</output>

<result>60</result>