Quantitative Aptitude - Arithmetic Ability Questions

The simple interest on Rs. 2000 for 2 years at Rs. 75 per thousand per annum will be

A train moves at the speed of 40 m/s and crosses a bridge of length 550 metres in 25 seconds. What is the length (in metres) of the train?

A certain sum of money triples itself in 5 years at simple interest. In how many years it will be five times?

A bookseller bought 500 text books for  20,000. He wanted to sell them at a profit so that he get 50 books free. At what profit percent should he sell them?

Prahlad has done 1/3rd of a job in 30 days, Sarfaraz completes the rest of the job in 90 days. In how many days can they together do the job?

If 9x - [5(2x + 1)/2] = 9/2, then the value of x is?

If cot A = n/(n + 1) and cot B = 1/(2n + 1), then what is the value of cot (A + B)?