A tap can fill a tank in 6 hours. After half the tank is filled, three more similar taps are opened. What is the total time taken to fill the tank completely?

What time is shown by the mirror if the real-time is 9:27?

During a month-long annual sale, a shopkeeper sells his goods at a discount of 50%. But in the last week, he offers an additional discount of 40%. If the original price of a shirt is ₹ x, then the price (in rupees) during the last week of the sale will be 

$$ \sqrt{217+\sqrt{48+\sqrt{256}}}=?$$

In how many different ways can the letters of the word ‘STRESS’ be arranged?

The marked price of an article is 10 % higher than cost price. A discount of 10 % is given on marked price. In this kind of sale, the seller bears: 

A mother is 28 years older than twice the age of her son. Five years later, the mother will be 10 years older than thrice the age of her son. What is mother’s present age?

A man standing on the bank of river observes that the angle subtended by a tree on the opposite bank is 60°. When he retrieves 36 m from the bank, he find that the angle is 30°. The breadth of the river is