The average age of a group of 5 members is 20 years. Two years later, a new member joins the group. The average age of the group becomes 20 years. What is the age of the new member ?
Pick one.
A) 20 years  B) 21 years  C) 10 years  D) 23 years  E) 24 years
The average age of a group of 5 members is 20 years --&gt; the sum of the ages is  5*20= 
<gadget id="calculator"> 5*20</gadget>
<output>100</output>
100;   Two years later the sum of the ages of these 5 members would be 100+5*2= 
<gadget id="calculator">100+5*2</gadget>
<output>110</output>
110;   Now, say the age of the new member is x years, so the sum of the ages of a new 6 member group is 110+x. Since given that the average age of this group of 6 members is 20 years then: 20*6=110+x --&gt; x=10.   Answer: 10 years.
<result>C</result>
The average age of a group of 5 members is 20 years. Two years later, a new member joins the group. The average age of the group becomes 20 years. What is the age of the new member ?