The average (arithmetic mean) monthly income of four workers is $2,600. After one worker’s income increases by 20 percent the new average income is $2,800. What was the original income of the worker whose monthly income increased?
Choose the most appropriate option: A) $4,000 B) $4,500 C) $4,100 D) $4,300 E) $5,000
Increase in total income was 200*4= 
<gadget id="calculator">200*4</gadget>
<output>800</output>
$800, we know that this increase was 20% (1/5th) of the workers original income, thus his/her original income was 800*5=$4,000.   $4,000nswer: $4,000
<result>A</result>
The average (arithmetic mean) monthly income of four workers is $2,600. After one worker’s income increases by 20 percent the new average income is $2,800. What was the original income of the worker whose monthly income increased?