The average weight of a class is x pounds. When a new student weighing 100 pounds joins the class, the average decreases by 1 pound. In a few months the student’s weight increases to 110 pounds and the average weight of the class becomes x + 4 pounds. None of the other students’ weights changed. What is the value of x? Choose the most appropriate option: A) 85 B) 86 C) 88 D) 90 E) 92
When the student weighs 80 pounds the average weight is x - 1 pounds;   When the student weighs 110 pounds the average weight is x + 4 pounds.   So, the increase in total weight of 110 - 80= 
<gadget id="calculator">110 - 80</gadget>
<output>30</output>
30 pounds corresponds to the increase in average weight of (x + 4) - (x - 1) =5 pounds, which means that there are 30/5 (  + 4) - (  - 1)= 
<gadget id="calculator">(  + 4) - (  - 1)</gadget>
<output>5</output>
5 pounds, which means that there are  30/5= 
<gadget id="calculator"> 30/5</gadget>
<output>6</output>
6 students (including the new one). So, initially there were 5 student.   Total weight= 5x + 80 = 6(x-1) --&gt; x = 92 pounds.   Answer: 92.
<result>E</result>
The average weight of a class is x pounds. When a new student weighing 100 pounds joins the class, the average decreases by 1 pound. In a few months the student’s weight increases to 110 pounds and the average weight of the class becomes x + 4 pounds. None of the other students’ weights changed. What is the value of x?