The average age of 40 students is 8 years. If the age of teacher is also included , then their average age increases by half a year. What is the age of the teacher? Choose one.
A) 45 years  B) 48.5 years  C) 28.5 years  D) 26.5 years  E) 29.5 years
Exp. Total age of 40 students = 40*8= 
<gadget id="calculator">40*8</gadget>
<output>320</output>
320   Let the age of the the teacher be x, Then (320+x)/41= 8+1/2 =8 ½.   320+x =17/2*41 =697/2= 
<gadget id="calculator">697/2</gadget>
<output>697/2 = around 348.5</output>
348.5, x=348.5-320= 
<gadget id="calculator">348.5-320</gadget>
<output>28.5</output>
28.5   Answer: 28.5 years
<result>C</result>
The average age of 40 students is 8 years. If the age of teacher is also included , then their average age increases by half a year. What is the age of the teacher?