A student cycles 2 km North, then turns West and cycles 2.5 km, then turns South and cycles 2 km, then turns to his left and cycles 4.5 km. Where is he now with respect to the starting position?
A mixture contains acid and water in the ratio of 7 : 3. If 4 litres of water is added to it, then the ratio of acid and water becomes 7 : 4. What is the quantity (in litres) of acid in the mixture?