The students participated in the tree planting activity and distributed 320 tree planting tasks to the fourth, fifth and sixth grades according to the ratio of 1:3:4. How many more trees are planted in sixth grade than in fourth grade?
同学们参加植树活动，把320棵植树任务按1：3：4分配给四、五、六年级．六年级比四年级多植多少棵？
<gadget id="calculator">1 + 3 + 4</gadget>
<output>8</output>

<gadget id="calculator">4 / 8</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">(1/2) - (1/8)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">320 * (3/8)</gadget>
<output>120</output>

<result>120</result>