Question

there are 20 children at a library 6 of the children have an average age of five years the remaining children have an average age of 8 years what is the average age of all the children at the library

Answer 1

Remaining children = 20-6=14 
So 14 children have age of 8 years old.

Average age = (6*5+14*8)/20 ≈ 7.1 ≈ 7 years old