Question 474726
The dollar cannot be added to $49 and $49. You can analyze this scenario by where the money flows:


You     Mom    Dad
0       50      50
100      0       0
3        0       0
1        1       1


You owe your parents $49 each, but this is independent of the $1 you have. If you had given your parents $1.50 instead of $1 then there would be $2 in missing dollars, this does not make sense either.