80 ÷ [48-{56-(60-36÷12×4)}]

6 litres are drawn from a cask full of wine and it is then filled with water. 6 litres of the mixture are drawn and the cask is again filled with water. The quantity of wine now left in the cask is to that of the water in it as 121 : 23. How much does the cask hold?

An octahedron has 12 edges, How many vertices does it have, 

A tank contains a mixture of 80 litre of milk and water. 70% of the milk and 30% of the water are drawn, therefore 55% part of the tank become empty. Find the initial quantity of milk and water in the tank.

Speed of train B is 20% more than speed of train A and length of train A and B is 720 meters and 600 meters respectively. If both trains running in opposite direction cross each other in 24 second, then find speed of trains B (in km/hr)?

What will come in place of the question mark (?) in each of the following series?

15     19    83   119     631     (?)

A tower standing on a horizontal plane subtends a certain angle at a point 160 m apart from the foot of the tower. On advancing 100 m towards it, the tower is found to subtend and angle twice as before. The height of the tower is