Solution to My Favorite Math Problem
The other one dollar didn't go anywhere! This is a counting trick! The $49 + $49 + $1 = $99 is a very clever counting trick to hide the remaining $1 which physically didn't go anywhere!
This is a numbers puzzle!
You borrow $50 from your Mum. You give her $1 back. You have borrowed from her $49. You have also borrowed $50 dollars from your Dad, paid one back and now owe him $49.
Your total borrowings are $98. You spent $97 and put the extra dollar in your back pocket.