Since girls on average get more money than boys, we shall assume that all the 250 children are girls. By doing that, we get $21 250.
However, that is more than the amount of all children which is $17 470. So, we have to subtract $17 470 from $21 250, we get $3780.
Then, we have to find the difference between the amount of all boys and all girls on average, which is $30.
We have to divide the excess amount of $3780 by $30, from which we get 126, which represents the number of boys.
Now, we are able to find how much in total the boys received, which is $6930.
With this, we subtract $6930 from $17470 in order to find how much in total the girls received, which is $10 540.
We are now able to get the answer by finding the difference between girls and boys, which is $3610, the answer.