The average weight of a group of boys is 20 kg. After a boy of weight 34 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?  Select the correct option
A) 12	B) 14	C) 18	D) 13	E) 10
Let the number off boys in the group originally be x.   Total weight of the boys = 20x   After the boy weighing 34 kg joins the group, total weight of boys = 20x + 34   So 20x + 34 = 21(x + 1) = &gt; x = 13.   ANSWER:13
<result>D</result>
The average weight of a group of boys is 20 kg. After a boy of weight 34 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?