A train of length x metres passes a man standing on the platform in 7 seconds. If the speed of the train is 72 km an hour, find x.

In how many minimum number of complete years will a sum of money put out at 25 percent compound interest be more than doubled?

A man can row his boat with the stream at 5 km per hour and against the stream at 3 1/2 km per hour. How much distance can he go in his boat in a lake (still water) in 2 hours?

Anita invested ₹8000 at 7 1/2 percent per annum for 2 years and 4 months. How much interest did she get at the end of the period?

A man and a boy finish a certain piece of work in 20 days whereas a man alone can do it in 25 days. It is found that the man does the work x times as fast as the boy. Find x.

The average age of 10 men is increased by 2 years when one of them, who is 25 years of age, is replaced by a new man. What is the age of the new man?

In what proportion must sugar at Rs.16.60 a kg be mixed with sugar at Rs.16.45 a kg so that the mixture may be worth Rs.16.54 a kg?

A man sold a book at a profit of 25 percent of S.P. The percentage of profit on his cost price of the book is ________.

The difference between the highest and lowest two-digit numbers is ________.