A woman walks 3 km North, then turns West and walks 4 km, then turns South and walks 7 km, then turns to her left and walks 4 km. Where is she now with reference to her starting position?
In a certain code language, '+' represents 'x', '-' represents '+', 'x' represents '÷' and '÷' represents '-'. What is the answer to the following question?
The weights of 4 boxes are 20, 40, 60 and 90 kilograms. Which of the following cannot be the total weight, in kilograms, of any combination of these boxes and in a combination a box can be used only once?