Pipe A can fill a tank in 16 minutes and pipe B can empty it in 24 minutes. If both the pipes are opened together after how many minutes should pipe B be closed, so that the tank is filled in 30 minutes?
A person invested Rs. 2,000 on simple interest for 7 years to obtain a total amount of Rs. 3,400 on a certain annual rate of interest. What was the rate of interest to obtain the above amount ?
A sum of Rs. 4,620 is to be paid back in 2 equal annual instalments. How much is each instalment (in Rs.) if the interest is compounded annually at 10% per annum?