A work is done by three person A, B and C. A alone takes 10 hours to complete the work but B and C working together takes 4 hours, for the completion of the same work. If all of them worked together and completed 14 times of the work, then how many hours have they worked?

Water flows into a tank which is 200 m long and 150 m wide, through a pipe of cross-section (0.3m x 0.2m) at 20 km/h. In what time will the water level be 8 m?

Ten different letters of alphabet are given, words with 5 letters are formed from these given letters. Then, how many such words can be formed which have at least one letter repeated ? 

Sandeep's salary is 20% more than that of Aron. If Sandeep saves Rs.720 which is 4% of his salary, then Aron's salary (in Rs.) is

An article is sold at a gain of 16%. If it had been sold for Rs.400 more, 20% would have been gained. The cost price of the article is

A and B can do a piece of work in 40 days and 30 days respectively. They worked together for 12 days after that B was replaced by C. the work finish in next 8 days. In how many days C can alone finish the work?

The sum of two digit number is 16. If the digit is interchanged the number is formed 18 less than the original number. Find the original number.

The average of nine numbers in M and the average of three of these is P. If the average of remaining numbers is N, then