The average weight of a group of boys is 20 kg. After a boy of weight 36 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?	Choose the correct choice from the following choices: A) 12 B) 15 C) 18 D) 24 E) 10
Let the number off boys in the group originally be x.   Total weight of the boys = 20x   After the boy weighing 36 kg joins the group, total weight of boys = 20x + 36   So 20x + 36 = 21(x + 1) = &gt; x = 15   ANSWER:15
<result>B</result>
The average weight of a group of boys is 20 kg. After a boy of weight 36 kg joins the group, the average weight of the group goes up by 1 kg. Find the number of boys in the group originally ?