For the past n days, the average (arithmetic mean) daily production at a company was 50 units. If today's production of 105 units raises the average to 55 units per day, what is the value of n? Choose one:
A) 8 B) 10 C) 12 D) 14 E) 16
The daily production was raised by 5 units for n days, which has a weighting of 5n.   5n = 105-55= 
<gadget id="calculator">105-55</gadget>
<output>50</output>
50   n= 10   The answer is 10.
<result>B</result>
For the past n days, the average (arithmetic mean) daily production at a company was 50 units. If today's production of 105 units raises the average to 55 units per day, what is the value of n?