Proof that girls are evil:
First we state that girls require time and money.
-> Girls = Time * Money
And as we all know "time is money."
-> Time = Money
-> Girls = Money * Money = (Money)^2
And because "money is the root of all evil":
-> Money = sqrt(Evil)
-> Girls = (sqrt(Evil))^2
And we are forced to conclude that:
-> Girls = Evil