There are 4 classes in the third grade of Sunshine Primary School, each class has 45 students, and there are 20 fewer students in the fourth grade than in the third grade. How many people are there in the fourth grade?
阳光小学三年级有4个班，每班有45人，四年级的学生比三年级少20人．四年级有多少人？
<gadget id="calculator">45 * 4</gadget>
<output>180</output>

<gadget id="calculator">180 - 20</gadget>
<output>160</output>

<result>160</result>