Sisters and Brothers

My daughter has many sisters. She has as many sisters as she has
brothers. Each of her brothers has twice as many sisters as brothers.
How many sons and daughters do I have?

Solution »

4 daughters and 3 sons.

For any particular daughter, she will have 3 sisters and 3 brothers. (DON'T count that daughter in -- she's the 4th girl -- otherwise it won't be 3 sisters = 3 brothers.)

But for any particular son, he will therefore have 4 sisters and 2 brothers. And 4 sisters are exactly twice as much as 2 brothers.