Answer:
The new average is
83
÷
26
=
3
5
26
exactly
83
÷
26
≈
3.192
to 3 decimal places
Explanation:
Assumption: None of the siblings are in that class.
Original numbers
25 students with 3 siblings each gives
25
×
3
=
75
siblings
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
New numbers
1 new student takes the total students to 25+1 = 26
The new total siblings is
75
+
8
=
83
The new average is
83
÷
26
=
3
5
26
exactly
83
÷
26
≈
3.192
to 3 decimal places