The average weight of 5 girls is 50 kg. If a boy enters their group, the average increases by 5 kg. What is the weight of the boy?

Step 1: Calculate the total weight of the 5 girls.

The average weight of the 5 girls is 50 kg, so their total weight is 5 girls * 50 kg/girl = 250 kg.

Step 2: Calculate the new average weight when the boy joins the group.

The average weight increases by 5 kg to 55 kg when the boy joins the group.

Step 3: Calculate the total weight of the group when the boy joins.

The total weight of the group when the boy joins is the new average weight * the new number of people in the group. So, the total weight is 6 people * 55 kg/person = 330 kg.

Step 4: Subtract the total weight of the 5 girls from the total weight of the group when the boy joins to find the weight of the boy.

The weight of the boy is the total weight when the boy joins - the total weight of the 5 girls. So, the weight of the boy is 330 kg - 250 kg = 80 kg.

So, the weight of the boy is 80 kg.