Three pipes A, B and C can fill a cistern in 10 hours, 12 hours and 15 hours respectively. First A was opened. After 2 hour, B was opened and after 4 hours from the start of A, C was also opened. Find the time in which the cistern is just full.

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

A crate of fruits contains one spoiled fruit for every 25 fruits. 60 % of the spoiled fruit were sold. IF the seller had sold 48 spoiled fruits, then the number of fruits in the crate were:

Sudhir and Shyam can do a work in 12 days, while Shyam alone can complete it in 30 days. In how many days can Sudhir complete that work alone?

What will come in place of question mark ( ? ) in the following series?
656, 352, 200, 124, 86, ? 

If cos²α + cos²β = 2, then the value of tan³ α + sin⁵ β is :

In a test consisting of 150 questions carrying 1 mark each, Saurabh answered 80 % of the first 75 question correctly. What percent of the other 75 question does he need to answer correctly to score 60 % overall? 

Two places P and Q are 92 km apart. A train leaves P for Q and at the same time another train leaves Q for P. Both the trains meet 4 hrs after they start moving. If the train travelling from P to Q travels 7 km/hr faster than the other train, find the speed of the two trains.