Question

There are 15 children at a birthday party.

The mean age of the 15 children is 7 years.
9 of the 15 children are boys.
The mean age of the boys is 5 years.
Work out the mean age of the girls.​

Answer 1

15x7=105 years
9x5=45 years for the boys
105-45=60 so 60years girls
60/6=10 60 years divided by the 6 girls
Mean is 10 years for girls