The average marks of a student in an examination is 63, if he had scored 20 marks in geography and 2 more marks in history, his average marks would have been 65. How many subjects were there in the exam?

The average of ten numbers is 72. The average of the first four numbers is 69 and that of the next three number is 74. The 8^th number is 6 more than the 9^th number and 12 more than the 10^th number. What is the average of the 8^th and 9^th numbers?

The average age of 6 members of a family is 25 years. If the youngest member of the family is 15 years, old then what was the average age (in years) of the family at the time of the birth of the youngest members?

There are 1600 students in a college, whose average weight is 50 kg. If average weight of boys is 54 kg. and average weight of girls is 38 kg. Then find the number of girls in the school.

While purchasing one item costing Rs.400, one has to pay sales tax at 7 % and on another costing Rs. 6400, the sales tax was 9%. The percentage of sales tax one has to pay, taking these items together on an average is: 

A certain sum is deposited for 4 years at a rate of 10% per annum on compound interest compounded annually. The difference between ihe interest at the end of 2 years and that at the end of 4 years is ₹5,082. Find the sum (in ₹).

The average of 6 numbers is 20. If a number is removed then average becomes 15. In place of removed number by adding a number 39 the average of new 6 number will be__

The average weight of 24 students is 35 kg. If the weight of teacher is added the average increased by 400 gram. What is the weight of the teacher?