The average weight of a group of boys is 30 kg. After a boy of weight 33 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?  Pick:
A) 4  B) 8  C) 5  D) 2  E) 9
Let the number off boys in the group originally be x.   Total weight of the boys = 30x   After the boy weighing 33 kg joins the group, total weight of boys = 30x + 33   So 30x + 33 + 31(x + 1) = &gt; x = 2.   Answer: 2
<result>D</result>
The average weight of a group of boys is 30 kg. After a boy of weight 33 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?