If the average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is: 

A company produces an average of 4000 items per month for the first 3 months. How much items, it must produce on an average per month over the next 9 months to get average of 4375 items per month over the whole year? 

Of the three numbers whose average is 60, the first is one-fourth of the sum of the whole number. The first number is: 

The average of eight successive numbers is 6.5. The average of the smallest and the greatest numbers among them will be: 

The average of the squares of first ten natural numbers is 

Some persons can do a piece of work in 12 days. Two times the number of such persons will do half of the work in 

Three vessels whose capacities are in the ratio of 3: 2: 1 are completely filled with milk mixed with water. The ratio of milk and water in the mixture of vessels are 5: 2, 4: 1 and 4: 1 respectively. Taking 1/3 of first, 1/2 of second and 1/7 of third mixtures, a new mixture kept in new vessel is prepared. The percentage of water in the new mixture is 

A retailer gets a discount of 40 % on the printed price of an article. The retailer sells it at the printed price. His gain percent is