Two planes start from the same airport. A flies 50 km East. B flies 15 km North, then turns East and flies 20 km, then turns to its right and flies 15 km. Where is B with respect to A now?
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 70, 50, 30 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?