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?

An examination was conducted for five subjects where the maximum marks for each subject was 100. Scored 82,97, 88 and 91 marks in 4 subjects respectively. If his total marks were 90 percent, then how many marks did he get in fifth subjects?

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?

The average marks of the students of a class is 68. The average marks of girls in the class is 80 and that of boys is 60. What percentage of students are boys in the class?

The owner of a bike buys petrol for 3 years continuously at Rs 64, Rs 80 and Rs 320 per litre respectively. If he spends Rs 32,000 every year buying petrol, what is the average price per litre of petrol?

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: 

The average weight of 8 people increase by 2.5 kg when a new person comes in place of one of them weighting 75 kg. What is the weight of the new person?